Them: Its not real money.
You: If a large number of people start using something and there is a demand for it, it has value and can be money.
Them: Where does its value come from?
You: For example to mine a bitcoin You need equipment and electricity, which is not for free. To mine one bitcoin, its costs You about 1000usd.
Them: You cant spend it
You: You can exchange your cryptocurrency in lots of places for usd or other fiat currency. And there are VISA debit cards available which you can use like regular debit cards everywhere.
Them: Cryptocurrency is not stable and you can lose money.
You: It is not as stable as usd yes, but that is because it has not big adoption yet. And you should not be worried about losing money, because the main trend of cryptocurrencies is been up for a long time now.
Please add some points to this to educate people :)