There is overwhelming evidence that the Holocaust happened. I, personally, can't believe anything else you say if you argue that the Holocaust didn't occur.
There have been lots of holocausts. I don't deny that Germany had an elaborate, industrialized process in place during WWII to kill Jews, Gypsies, Poles, Russians, the mentally ill, anyone who spoke out against Hitler, etc. but I'm saying calling that THE holocaust, because Jews were involved, is wrong. There have been MANY genocides during the 20th century, some that dwarf even the numbers (roughly 6 million Jews, 5 or 6 million others). I fail to see how one genocide is more important than another.
Also, putting "the" holocaust into Catholic doctrine is wrong. ALL genocides should simply be brought together as crimes against humanity that should be condemned, no ONE should be put above others.