(note the correction) Perhaps because they don't understand the complexities of how a person may feel, unless the person is 'exactly' like them. Christians have inherited a very simplistic view, as a result of adhering to a text written for common folk, edited by those in power at the time. The aim was to unite people under a common belief system which was easier to manipulate than allow diversity of thoughts which could only lead to chaos.
So the simplistic view does not make room for these complex issues. Personally I think if there is some omni-potent being, then clearly all beings are part of it. No one can be 'outside' that omnipresence.
To judge and condemn is discouraged in christianity yet it would seem they are the most judgemental of all. Infact they have fractured the fabric of society by making so many divisions, forcing christianity on the indigenous people, subjugating women, enslaving people of African heritage, Wars etc. Its no surprise they do not make room for transgenders, homosexuals etc (although they have no qualms employing pastors who violate children). Such is the glorious story of Chistianity.
Many people don't accept them. Many are just scared to say anything because in america you get called all the words under the sun if you don't agree. Go outside America and see what people have to say.
Science doesn't accept them. It's a persons right not to accept it,but he does have to treat with the same respect. Just like for an aithest,it's his right not to be a Christian,but still have to treat with respect.
To answer your question,Christians are not allowed to hate anyone. Believe anything they want,Just love and treat everyone kindly. Which sadly,is not what many Christians do.
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.