Why are/do people so afraid of/hate different belief system and other races/sex/sexuality etc?

It's not a "majority of people in the world" - unless maybe if by "the world" you mean "the USA". You are correct that "black" and "white" are merely skincolours. As to why people believe that races exist... I think those government forms in whcih you are asked to state a "race" is one of the reasons, and the lies of some demagogues are another.

You must not pay attention, do research before you ask questions on here. Also people come to those conclusions because they are statistically correct most people in certain races are known to be a certain way therefore people make a judgment call on that. "White people are evil" is a racist comment though, just because there is no statistical proof in that assumption.

Not all black people are violent, that comment is just based on statistics... a higher percentage of black people are more violent if compared to other races, according to reported incidences.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.