What Would You Do (Unfortunately I can't ask Jesus and get an immeadiate reply)

So what would you guys do if one of your friends, that you maybe kinda like and were thinking about taking to a dance is actually not (ummm how should I put this?) who you thought they were? Like there whole lifestyle isn't what you thought it was. And it's not something small and as inconsequential as, uh let's say breaking the drinking law every now and then (not that I'm saying that's acceptable......). I'm talking things like they're complete jerks, or they don't like the gender you thought they did.... you know... stuff like that.  And this lifestyle difference is something you are entirely against (to the extent of Civil War type dislike).
See, I have this situation. Right now. I've got no clue what to say, what to do, or who to turn to. And I want to support this friend of mine (and keep them as a friend) but I want to let them know how wrong what they are doing is. So how do I do that? How I tell someone that I hate what they're are doing but still like them as a person?