You are prejudiced against atheists to think it needs to be proven. Just as you would be prejudiced against blacks if you thought it needs to be proven that blacks are not morally inferior to whites. I have learned that it is pointless to try to change the mind of a prejudiced person. He must decide on his own to give up his hatred. The choice is yours. I can't make it for you.
Here is the difference though. Atheism isn't a skin color and for you to make that comparison is totally irrational. Such a tactic is akin to Godwin's Law and a shame that you would use such a cowardly way to get out of proving your point.