Well... Seriously threatening to shoot a family member for almost any reason is likely to land one in trouble.
As far as hypothetical (at this point) involvement in DC goes, what would you say if “Dad” is on camera following a crowd overrunning a barrier and he goes into the Capitol building?
I would say that he’s no longer exercising his first Amendment rights and is taking part of a riot.
If he’s taking part in the riot, he should be charged with what can be proven.