@Doomer Racism is NOT not liking a race, it is the feeling of superiority over other races, the thinking that its your right to rule or annihilate them, to be above them. Of course it is dumb in the first place to "not like a race", because a race isnt an individual, but a group of many people, so as long as you dont know every single one of them personally its idiotic to "not like them", but you can do that, as long as you dont think that you are better/more worth and can do with them what you want.
To the las question: I personally do in extreme circumstances, yes, if someone had "murdered" Hitler and his helpers, than millions and millions of the so called "subhumans" in their eyes wouldnt have died. Killing someone to prevent them from starting wars and murdering innocents is ofen a thin line, but nonetheless the right thing to do.