SUBREDDIT: r/relationships
TITLE: His parents don't like me because I dated another girl in the past. What do I do?
POST: He's 17 (m), I'm 16 (f). Been pretty good friends since 7th grade (we're now juniors) and have now been together for a month and a half or so.

Backstory: in freshman year I dated a mutual friend of ours, a girl (was an experiment of sorts, kinda complicated, unimportant for now) for 3 months. It caused a bit of controversy amongst parents and friends because of the whole lesbian thing and when her dad found out, she broke it off.

Now, the guy is fine with that. His parents aren't. They (according to him) think of me as contaminated and generally don't approve of me, purely because I dated a girl as far as I know - it seems to stem from homophobia alone. I'd met them a few times before I got with this guy and they were fine with me then. I believe their disapproval of my past choices is due to religious reasons.

So my question is, how do I approach his parents? Clearly they do not want their son spending time with a contaminated person such as myself (the mother much prefers his ex gf to me). I kind of want to talk to them about this, but then it's not really my place. I get the feeling it's going to get in the way of me and him down the track. They've prevented him from seeing me a couple times now, I think, and I feel it's going to happen again. Since this is a high school relationship I'm not pinning my hopes on this one guy forever, obviously, but I really would like to do something about his parents hating on me right now.
TL;DR: 
his parents don't approve of me because I dated another girl a couple of years ago and they think I'm 'contaminated' etc. and I would like to do something about it but don't know how.