No this ONE incident by itself isn't a dealbreaker. God reddit's completely unforgiving standards for people on this sub never cease to amaze me. Redditors aren't fortune tellers who can say everything about your bf's future based on this one minor incident and it's fallaciously presumptuous to try. Who's to say it wasn't some knee jerk reaction upon literally WAKING up? Who's to say he can't adjust?

It was quite immature but also only ONE incident (as far as we know). Just have a talk with him and explain that his reaction was excessive. If he cares about you, there's a decent change he can adjust to the realization (or MAYBE he already knows it was a knee jerk reaction) and then you didn't have to lose the relationship over fucking nothing like reddit suggests! Everyone wins!

Now, if he defends his reaction as justified, even in a calm, rational discussion despite your side of things, THEN you can make an accurate judgement call if this incident is truly telling of an incompatible personality.