To take your earlier example, that the holocaust can be considered 'universal evil', did you realise that there were something like 1.5 million people in Germany at the time?
Do you think all the German soldiers, administrative staff, Nazi party members, Nazi party supporters, all thought 'yay we are being evil'? Or do you think they thought they were doing the right thing?
At that time, for the Germans involved, the holocaust was right.
I guess the holocaust is truly an example of just how diverse morals can be, your ultimate evil was looked upon by some as the saving the world.