Can you be a horrible partner but still be a decent person?

So I have a few guy friends who are actually the worst type of guys when it comes to relationships, they're cheaters, drug dealers, one is even physically abusive but they're actually so good to me because I'm obviously not in a relationship with them. Anyways so my friend and i were discussing this and she refuses to believe they're decent guys because of the way they are with the women they date. I don't condone their actions at all but they've always been good to me, they've always been there when I've needed them, everytime I call them for a favour, they drop everything and come running, the guys I've dated wouldn't even do that for me.