thats between you and him, the heck with your friends
I have been talking to this guy for awhile. And we like each other.. My friends don't really approve of him, because of his past. How can I show them that he's changed and he actually respects me?
If he has changed. His behavior, words and actions will convince all. Or not 😉
He's earned your respect---he's going to have to do the same with your friends.
Be sure his past is separated from his (and your) future.
I'm sure your friends have your best interests in mind. Sometimes, when we're "smitten" with someone, we just don't see them objectively. Just because you've been talking with someone for "awhile" doesn't mean you know him well. Have you spent time with him in person?
I would proceed cautiously ... Just in case your friends are sensing something you're not.