Have you ever wondered why people say the Jewish Holocaust never happened?

I have wondered about this and I have come to believe that part of it may be the constant reminding of the event. I believe it happened because I had a older cousin who was captured by the Germans in the war and was in a prison camp for a while and came out weighing 70 lbs and he told of events he saw there and many other things such as speeches by the Nazi's make it obvious that the Jews were hated by the Nazi's. But many other races of people have had m killings of their people and you don't here much about it, such as the 40 million mostly Christian that Stalin had killed or worked to death and think of the many other kinds of people mistreated thru history. There is a Holocaust museum in every major town in the USA and you here of it constantly while other terrible things that happened to other kinds of people don't get near the coverage, You know how people get annoyed by whining, do you see my point? I mean yeah it was bad, I do feel sorry for them.