1. You're a mean person.
I don't know how many people I've met who simultaneously claim to be Christian yet are consistently hurtful to other people and who seem to take genuine satisfaction from tearing other people down. I cannot fathom how one brain can cultivate and contain enough cognitive dissonance to be mean and still claim to be a Christian. If Jesus really died for your sins, you'll be the first to get thrown in Hell, not just for the inexcusable way you treated God's children, but also for how irreparably you soiled Jesus's name with your petty behavior.
2. You own expensive luxury items.
I've seen Jesus fish car magnets on Hummers, BMWs, Cadillacs, Mercedes and every other luxury automobile I'm too poor to afford. I've heard self-proclaimed Christians brag about how many Gucci purses they own. I've seen pastors wearing suits that cost more than my entire wardrobe. I've seen people wearing 24 karat gold "WWJD" jewelry without expressing a hint of irony.
I must have read a different Bible than these people, because in the one I read Jesus was penniless and consistently urged his followers to give up everything they owned so they could devote their lives to helping the poor. Owning expensive luxury items is so opposite of everything Jesus stood for that I can't even really articulate how hypocritical that is other than to just repeat what I just said slower and louder.
Obviously you've found some way to reconcile your hypocrisy in your own head and would be more than happy to use it to shoot down my accusations, but honestly, if you had that argument with Saint Peter at the pearly gates do you think he would be impressed by your mental gymnastics? He would probably tell you that a camel has a better chance of fitting through the eye of a needle than you do of entering the kingdom of Heaven. If you're going to choose the way of the world then just run with it and live it up while you can. Quit wasting your time with pretenses.
3. You spend more time sitting in church than you do working in charity.
How many times did Jesus enter a church in the Bible, and what did he do when he was there? Off the top of my head I can only think of 2 times he ever entered a church. The first time he was a child, and he was telling the religious leaders they were fools for putting too much importance on the law and not enough importance on people. He returned to church as an adult and went on a rampage over how profit-centric the church had become.
What about you? Do you just punch your time card with God every Sunday and then get back to taking care of your own family? Have you ever eaten with a homeless person? Did Jesus set up a $50 recurring direct deposit to the Roman equivalent of the Salvation Army and call himself a martyr? No.... because that's borderline pointless, and if that's what you do then it's pointless to call yourself a Christian.
4. You habitually indulge in self-gratification.
I've had multiple religious arguments with self-proclaimed Christians while they were holding a beer in one hand and a cigarette in the other. Their justification was that Jesus never said you couldn't smoke. True. Jesus also never said you couldn't buy season tickets to your favorite sports team. Jesus never said you shouldn't watch professional wrestling. Jesus never said you shouldn't eat so much processed food it gives you diabetes. Jesus never said a lot of things, but he did live a distinctly ascetic lifestyle.
Do you live a distinctly ascetic lifestyle or do you live more sumptuously than 2/3 of the world's population? If you have to make excuses for your relative decadence, I don't want to hear them because really, the only point in trying to justify yourself to me is to justify your actions to yourself. Tell your excuses to God. He's the one you're going to have to answer to anyway. But until you see the Lord face to face, you may want to stop telling people you base your life on the example Jesus set.... because you don't, and it's blatantly obvious to everyone but you.
5. You're prejudiced.
Not all self-proclaimed Christians are prejudiced, but enough of them are that prejudice and Christianity have become synonymous. Hitler used Christianity to justify persecuting the Jews. The KKK used Christianity to justify persecuting African Americans. The Westboro Baptist Church uses Christianity to justify persecuting homosexuals. These examples aren't isolated anomalies. They're merely the far extreme of a broad spectrum of intolerance in the name of Jesus.
Having said that, nobody would argue that Jesus was an intolerant, xenophobic racist at the end of his life. You could even argue that blind acceptance of our fellow man was the crux of his message. So if you're in favor of closed borders, segregation and the persecution of sinners and dissidents, find a different group to identify with than Christians, because that's just not fair to people who do actually emulate the egalitarian beliefs and behaviors of Jesus.
6. You don't live in an egalitarian commune.
To be a Christian is to be Christ-like. This makes being a Christian hard, because from the time Jesus started his ministry, he basically lived as a traveling beggar and public speaker until his death. This isn’t a lifestyle choice we can make a categorical imperative out of. If everyone in the world sold everything they owned and travelled the world preaching to each other, the human race would die off in a generation from lack of productivity. So this is one instance where you really have to disregard Jesus's example a little. This raises the question though, how much should a good Christian tone down Jesus's fanaticism to arrive at a level that's sustainable while still honoring the spirit of Jesus's teachings?
Given that Jesus was penniless and an adamant advocated of asceticism and austerity, I would say that living in a $250,000+ house with a huge entertainment system in the living room, a luxury automobile in the parking lot and a golden safety net in the bank would be an extreme example of how not to be Christ-like. I would argue that Paul was closer to the mark in how he lived communally with his Christian brethren, owning nothing and sharing everything equally (Acts 4:32-35). I certainly can't find any reason why Jesus would object to egalitarian communal lifestyle, but don't take my word for it. There are millions of monks all over the world who have come to the same conclusion.
7. You're a pedophile.
You can be a child rapist or a Christian, but you can't be both. If you try, you'll only disappoint Jesus and hurt your entire religion's reputation.
8. You support the military.
Jesus said if your enemy strikes you then you should turn the other cheek. However, I've heard it argued that Jesus intended to mobilize an armed insurrection against the Romans, but even if Jesus did support military action against the Caucasian, western imperialist nation that was building permanent military bases in the Middle East and setting up puppet leaders in the local governments, that would still set a precedent that Christians should stand opposed to military aggression, particularly in the Middle East.
Then again, Jesus never did lead an insurrection. He preached peace and allowed himself to be killed by Israel's enemy even though he had the power to smite anyone. I'm not saying you shouldn't own guns and defend your house. Just don't call yourself a Christian. You certainly shouldn't call yourself a Christian if you serve in a military that actively invades other countries. If you’re are in the military, you probably justify it to yourself by saying that you're fighting for freedom, and that's fine. You can call yourself a hero for that. Just don't call yourself a Christian. If you aren't in the military, but still support the military and the troops who do the killing, then by all means, call yourself a patriot, but don't call yourself a Christian because you're advocating the opposite of what Jesus advocated.
9. You don't speak Aramaic, Hebrew or at least Latin or Greek or have an intimate knowledge of ancient Middle Eastern history.
I'm not saying that just because Jesus spoke Aramaic that you have to speak Aramaic too in order to be Christ-like. What I am saying is that in order to think and act like Jesus you need to understand where Jesus was coming from. The better you speak the language he spoke in, and the more you understand the culture he was raised in, the better you will understand his message. The less you understand these things the less you’ll understand his message and thus the less chance you’ll have of being able to follow his example. The less you understand the original context of the Bible the more you’ll subconsciously project your own context into it. When you do that you end up reading what you want into the Bible, and all your Bible study does is serve as a mirror with which you justify to yourself the modern values of the culture you were raised in.
In other words, don't claim to be a die-hard, card-carrying member of the Shakespeare fan club if the only thing you know about Shakespeare was what you gathered from watching the Leonardo DiCaprio version of “Romeo and Juliet.”
10. It's been thousands of years since Jesus died.
It's been 2000 years since Jesus supposedly lived. You live a life of luxury and privilege. You barely know anything about Jesus's life and environment. You spend more time making excuses for why you don't live like him than you actually do living like him. The only real Christians are Biblical scholars living in monasteries, and they're no use to themselves, God or anyone else. They're living in the past while you're pretending to. Give up the charade. Admit you're not a Christian, and take a more reasonable, logical, scientific approach to understanding the universe and improving yourself.