It sounds to me like the guy wanted to let you and everyone else know that HE "knows" you are bi or gay and HE is NOT. It may be more about HIM letting people know that he is NOT gay rather than a reflection of how he feels about you. I don't think he meant to hurt you but I can see how you would be hurt by his thoughtless comments. I would also guess that someone may have told him about your bi-ness. Gossip like that spreads like wildfire. But you did say that you were o.k. in telling people. Just know that there are plenty out there who are insecure about there own sexuality and need to go to extremes to "prove" they are a "real man". That's just my take on it. If you like this guy, I'd try to let him slide. However, if he continues with his "jokes", I think you'd have to have a word with him on the side letting him know his remarks are uncalled for and only make him look like a fool.