If we're still doing "What would Jack Kirby think?" question then Evanier covered that
as best he could.
tl;dr Jack was a soldier; he didn't just punch nazis, he killed them. He didn't go around punching nazis after the war ended. If someone challenged him to a fist-fight he wouldn't back down (irrespective of whether the other party was a nazi), but he didn't punch guys in the back of the head. Of course, he's not around to tell us his feelings on the subject in the current political climate.
I am not sure what Captain America's other creator, Joe Simon, would have had to say on the subject. It is entirely possible that he would have a different view from Kirby's.