Always end up being the bad guy

My boyfriend's best friend is a big coke head. I really don't care because he isnt my problem and my bf doesn't touch the stuff. The friend never gets violent or crazy, he's actually a pretty decent guy. To each their own I guess. But I found out that my bf let's him use the shit in our home. Now I'm worried about him ever coming over once the baby is born (babies can die from that stuff soooo easily) but he's also my bf's only good friend. I'm tired of being the bad guy but he hangs out around people doing no good for themselves, it's so frustrating.