I come from a family of Holocaust survivors. My mother was raised in Israel. My grandfather lost his wife and daughter in the Warsaw Ghetto, and my Grandmother lost her husband, parents, and sister - she jumped off the train to Auschwitz and was lucky enough to dodge the German bullets until she made her way to the relative safety of a former Polish boyfriend's house in Warsaw. One of the things that amazes me is that the Holocaust is one of the most important historical events which is constantly being "denied." Most people wouldn't deny that the Turks slaughtered Armenians before WWI or that US Cavalry Troops massacred Native Americans. No one denies that the Tutsi in Rwanda killed the Hutu. Why then do people run around denying the Holocaust?
Part of it stems from the very accusations made against Jews in the first place (and this is what makes denying the Holocaust so reprehensible) - the belief that there is a secret Jewish media conspiracy to control the world, and that Jews manipulate Western public opinion in order to get their way. Those types of accusations were being leveled at the Jews during World War II and are even to be found in Mein Kampf. This being one of the main accusations that anti-semites make against Jews, it stands to reason that those dastardly Jews would make up such a horrifying event in order to profit from world opinion, wouldn't it? This is similar to the accusation that the Jews really blew up the World Trade Center in order to get the US firmly on the side of Israel.
There's as much historical evidence of the Holocaust as anything that happened this century - German records, Austrian records, US army films, eyewitness testimony, including that of Germans (look for instance at Claude Lanzmann's excellent documentary "Shoah" where he interviews SS guards as well as survivors) - in fact, there may be slightly more evidence than that of most historical events, because the people at the time knew that they were witnessing something amazing. (If you go into the US Holocaust memorial, the first exhibition is a clip of General Eisenhower saying that he ordered Dachau to be filmed immediately by the US Army Corps of Engineers because otherwise "people would say that things like this just don't happen.") Or just go to any good library and read a transcript of the Nuremberg trials. Why, then, is this even targeted for non-occurence more than others? Because of the same belief system that helped the Holocaust occur in the first place - the belief that the Jews are a shadowy power, able to create what would be a hoax wildly out of proportion of any hoax in the world.
I am normally not a fan of political correctness but let me tell you - tolerating denials of other people's tragedy backed up by a mountain of evidence has a very harmful effect of the people who went through that tragedy. Being Jewish, and wrestling with the Palestinian problem, the constant attacks on Israel in the media, etc. most people wonder whether or not we should be more/less in favor of peace, etc. Some Jews even wonder whether or not we can trust any non-Jews at all. Get close enough to a Jew and he may even tell you that because of the Holocaust, almost every Jew is ready to pack his bags and flee, no matter where he may live. People denying large portions of our history in the name of "free speech" or "not being politically correct" is something personally harmful to every Jew. It would be as poisonous and ugly as going to an African American and saying, "you know, slavery wasn't really a bad institution for blacks" or telling a Native American, "sure you were slaughtered but YOU attacked us". In fact, it is a form of being utterly impolite. It makes us paranoid and irrational at times, and is pretty much a sin. Criticize Israel for whatever event you want, say whatever you want to about Jewish history, but to deny the obvious - that millions of us were massacred in Europe because we were accused of secretly running the world, which we obviously were not doing - is a sin. And I for one, am surprised that any church would specifically invite anyone in order to get up on the pulpit and sin in public. I would tell you that such a person belongs in a Satanist Church, but honestly, I wouldn't want to insult Anton Szandor LaVey.