i dont understand why you would have to stop being his best friend. being straight edge is a personal choice just like using drugs is a personal choice. if your friend wants to use drugs or drink, etc, you should respect him enough to let him make that decision. the only reason i can think of to cut yourself off from him is if he becomes hegemonous with his drug usage and comprimises your choice to maintain a straight edge lifestyle cause if he is truely your friend he will not try to interfer with your ability to live this way without having to deal with pressure to give it up. plus sometimes people break edge cause they are going through a tough time or the pressure from outside influences is too much and the support of a good friend will be enough of a help to let them get back on the horse and realize that they don't have to go it alone and that you will be there for them whatever the outcome is.