First of all I will say that I am not christian and have no need for religion in my life.
I am interested in what you say, this is not an attack, just an observation.
You say that christianity mentality is bad, and that they think they are better than anyone else.
But, in labelling them bad you are putting yourself in a stance in which you view yourself better than them, and so it cant be resolved wither way.
People judge the world based on there experiences, which is fair enough. but if we look at our experiences we can see that they are limited. that we have not had every experience there is to be had and so our judgements are created from incomplete information.
If we realise that imperfection is created by comparing the world to how we believe it should be, and that these beliefs are limited we can let go of the beliefs, and therefore judgement, and become in harmony. which is the aiki way
and if you look into christianity closely without the dogma then you will find amazing similarities.