Self-awareness and maturity allows one to feel emotion without displaying it in a way that makes other people uncomfortable or appears disproportionate, out of context and unhinged. If the guy reacts like that to a teaser trailer... how can he escalate for the full film... or the birth if his first child. Is there some displacement going on, a personal trauma which is feeding this reaction?
We stop children from expressing themselves freely because that type of behaviour is often antisocial - that's not how to behave socially. It isn't repressing anyone to say - maybe you shouldn't record yourself having a total breakdown over a 30 second movie clip (of which very little was actually shown). I'm not saying that to be a dick, but this isn't a healthy response.
I'm not cutting down I'm legit concerned for them. The way this person portrays themselves may impact their interpersonal relationships and other facets of their life.
I suspect there's a psychological or comprehension problems if you're regularly crying over reveal trailers.
You're assuming this guy or any other who can react like this doesn't have the moral code needed to know how to act in public, which is, again, judgemental especially when you don't directly know who you're talking about. Who tells you this is how he acts in public ? How he acts in social circles, outside of his own home ? He may be "overreacting" for a 30 seconds movie clip, but you're assuming his complete social behaviour based on a 30 seconds clip of him. It sounds kind of ironic, if you ask me.