Check Thor and Captain America and tell me what you think.
I've mentioned it before, but my all-time favorite issue of CA came out in 1968; the first appearance of Dr. Faustus. In this issue Cap keeps having flashbacks to the war and going into insane, uncontrollable rages. After a while he figures out it's his psychiatrist, who is evil and plotting against him.
Jack Kirby was not a well man. We forget, since we have enshrined him, that part of his appeal was seeing what random, lunatic shit he would come up with next. I read an interview with him once (sorry, no citation) where he said that he research his comics by watching people walk by and trying to figure out how to beat them up.
Another thing they don't mention much was his legendary temper.
But that's neither here nor there -- the point here is that Kirby strongly believed, like da Duke, that young folk should register and fight for their country, and if they did not they were morally reprehensible. Again, I think his Thor issues have the best illustrations for this.
By the time of Forever People he was more-or-less over the political and had moved on to the cosmological, so look for earlier stuff.