Most Helpful Guy
Because he's still hurt. He's not doing it purposefully. He is still hurt. He hasn't been able to "forget".
Some people can forget, others cannot. He is clearly the person that can't forget. But look at it this way, so what that he brings this stuff up, that's his insecurity now that he is showing you. If you can work through that, I guarantee you, your relationship after will be stronger then what it was before.
If you really wanna be with him, work through his misery this one time. But after when you had said "im sorry", or "yes I get what I did wrong, and it won't happen again". Then he has to promise you to not throw stuff like this in your face after. And I'm pretty sure he wont. He's just getting past a little hurt he has. That's all. Just work through it and everything will be fine. I promise.