Now I am not saying he is not, but what basis from what has been posted here do have to conclude that?
A clever young man would not need to ask the question he asked honestly.
Well, clever is as clever does.
Nitpick: “… who is in the wrong.” You’ve got an “is” there. You need the subjective case, not the objective case. The case is determined by the role that the “who/whom” plays within the clause.
Hitler, in his sick attempts to purify Europe of the inferior peoples, killed a staggering number of fellow European white people.
If he would have succeeded in conquering and holding Europe, considering what he did to other Europeans, what would he have done to the peoples of the Middle East?
Your father is justified in his anger. Hitler was a cancer to humanity.
Find another way to piss him off.