No I do understand it. I quote: "the rule has more to do with completely losing one's sense of proportion rather than just mentioning Nazis specifically"

I think your sense of proportion went out the window when you brought Trump (I could probably have forgiven the Hitler bit but you married them.) into a comparison with Apartheid era leaders and their policies. As has been mentioned here there was no program to eliminate the black population. There was a program of separate development which had the desire, at least initially, of being to the benefit of ALL groups. Also you forget that there was a war on against marxism and those that "fell" out of windows were soldiers/supporters fighting for a Marxist state. War is ugly- people die. You like many others seem to confuse the war part with the social part of that era. 

Apartheid era businessmen donating printing services to a political party leads to Leopold/Hitler/Trump references....Ok I concede- Godwins Law was a poor choice.