Well I don't know what the Capt. America movie is like nor have I read about it etc.
However, I have a 7 year old son.
He has watched all the Iron Man movies. It is PG-13. He was fine with it. No nightmares after etc. He loves Iron Man.
He knows... what fiction and non-fiction is. Even from when he was younger.
Sure, the "imagination" development of kids vary.
But, I don't know if I would compare... a "Bloody Mary" movie to a superhero movie.
I mean, *I* don't even want to watch a Bloody Mary" movie. I HATE horror films. Myself. Even my middle school aged daughter hates those.
That genre of movies, horror films, is... not something to have a 7 year old watch. So no wonder your son got NIGHTMARES from that movie.
I would too.
Now- does your son like "super hero" stuff?
Does he watch cartoons like that or whatnot?
IF he is not even interested in things like that, then why... take him to a Capt. America movie?
Unless, it is just about keeping up with the Jones' type thing. ie: other kids talking about it, so then your Husband wants to take him to it.
But just because others see that movie, it doesn't mean your Husband has to or your son.
Next: Why, does your Husband want to take your son to the movie? Because HE wants to see it? Or does your son want to see it too?
And sure, per the rating of the movie, well, you know what that is.
So, if your Husband wants to see it, but your son does not or is ambivalent about it, then don't take your son to see it. Or does your Son want to see it... because he wants to "please" his Daddy and thus will just agree to going, no matter what?
And these are... typical scenarios which may happen, per young children. And their parent.
So, DISCERN this. Per your son. And then, with Husband.
And it is not like ALL kids, have to see this movie.
I work at a school, elementary. And there is no way all boys have to see this movie or want to. I know kids who don't even care. Some do, because all the other kids are seeing it too. And besides that, the kid doesn't have any reason why THEY want to see it.
It is just because others are seeing it.
But if a kid does want to see a movie, the parent has to see what is best for their... child and per his/her own comprehension and disposition.
Per the movie rating etc. and all that.
Why don't you ask your son himself, IF he wants to see the movie anyway. Or if he is just doing it to please Daddy.
It is hard for a young kid, to say they want to watch a particular movie... when they have not even seen it, nor their parent.
Movie theaters are also loud. The sound is loud. Too loud for even my kids sometimes.
A child, can also, close their eyes and ears... when/if violent or inappropriate scenes, appears. But is that doable? Or not?
If my 7 year old son wanted to see it, I would let him.
My Husband would take him.
Its fine.
My son loves Super Hero stuff/Marvel and is fine with it.