Just because everyone is doing it does not mean it's ok for you to do. Even if everyone involves your Christian friends or your role models. No one is perfect so you can't use them as your excuse for doing whatever it is you know you shouldn't do. Don't use anyone as a standard for how you should act use Jesus. You will always fall short and you will never think that however good you are doing is good enough. There are always places you could be better and using people as standards for how good you are will make it hard to realize where you need to improve. Just because Christian friends are doing it doesn't mean it's ok, it just means they have a flaw they need to work on just like you do. It's harder to avoid doing something when your friends are doing something bad because after being around them doing it you slowly start to forget why it's so wrong and we subconsciously start doing what our friends do. So if your friends swear then it is much harder to stop yourself from swearing, which is one reason it's good to have friends who have the same standards you do, but it doesn't make it any less wrong.