How can i tell my boyfriend to stop?

so my boyfriend of almost 2 years, has been chewing tobacco for almost like 6 months now, and i really dont like that he does. i dont want him to continue doing for years to come. i have done it a couple times with him, but i just want him to stop now. hes getting more and more into it and i dont know what to do. All his friends do it too ,and they are what got him tos tart doing it. but hes not the kind of person who cares what people thinks. he would care what his friends thought of him if he decided to stop chewing, so i dont think that part would be the problem. i jsut dont think its god for him and i want him to stop chewing tobacco. How can i tell him so that he will stop, and not be angry with me?