This is one of the reasons why most teenagers rebel. Peer pressure is hard to overcome. In this situation, it is better to stand on your principles. What is wrong will always be wrong, unless you like the idea too. Don't worry if you'll loose a friend for not agreeing with him, you don't deserve such kind of friend in the first place. It is better for a person to choose his friends. The saying "tell me who your friends are, and I will tell who you are" is indeed true, use this as a guide for choosing your peers.