I am a pacifist, but I support the 2nd amendment in the United States. At the same time - I agree with you for the most part. Including about restricting weapons from certain immigrant groups that have a history of violence for cultural reasons. But their children would have the same rights as everyone else.
I don't think it is legal to own a grenade launcher in the United States; I also wonder why we don't raise the age to buy a weapon to 21 given that we don't let kids drink before then. I am on the fence about AR-15s since there are cases, one recently in Texas, where it was used by a trained civilian to save lives.
The real issue for me is the lack of training - yes, there are conealed carry and weapons safety classes people can take but they are not required.
I think the reason is the history of racism - once upon a time, for example, blacks were discouraged from buying guns in America and had to pass a difficult test to vote.
Martin Luther King Jr. was denied a permit to carry a gun.
So there is a fear that if we imposed what I consider sensible rules that those rules would be used to deny certain groups their rights.