An orgasm is like a sneeze. There’s really no way to have any control over it.
And seriously, even if you did “orgasm gracefully,” what would he gain from that? A slight aesthetic benefit? “Oh, that looked/sounded nice.”
Having an orgasm is one of the few times in human life where you shouldn’t have to worry about what other people think of you, or anything. Bringing someone to orgasm is supposed to be something you do for that person, because you care about them.
The sentiment he expressed was basically, “that didn’t look nice.” Even if he didn’t mean it, it’s kind of a dick move, because he put his own (minor) aesthetic concerns ahead of your well-being. He made you feel self-conscious about the one time where nobody is supposed to feel self-conscious. It was a selfish thing to say.
It sounds like you really like him, and that’s fine, but he might have a hidden undercurrent of dickishness or selfishness. Sometimes the things people say unintentionally can be really telling about their real personality. That’s especially true early in a relationship, when otherwise they’re trying extra hard to impress you. I would keep an eye out.