Some of the rudest people I've met while traveling, are in the hostels. They stick to their own groups, and when a outsider interrupts for just a second to say hello, somethimes they get all condescending about it. Sometimes people are tired and emotionally worn out, but some travelers alone are lonely, and need someone to share their emotions with. Even if someone seems odd to you, it's good to make them feel welcome, because they have spent a lot of money to go on their vacation, and their time is just as valuable as anyone else's. We don't have to accept all forms of bad behavior, but we need to develop a culture of lieutenancy, and make the enjoyment of the trip a higher priority over being hard on others who mess up a bit.