Nothing. For all I know maybe it didn't. There are arguments based on empirical findings people have made that the holocaust didn't happen, or at least didn't happen in the numbers it's believed to have. Supposedly 16 million Jews died in the holocaust (or at least that was the accepted story for many years, I think they may have updated it), and I read once that the Jews had used the number 16 million multiple times in the past wrt their claims of persecution.

I know saying the holocaust may not have happened is offensive, but it seems to me that that's only because society is under some strange spell where the canonical account of the holocaust is seen as sacred ground. For example, I tried debating this with my mom the other year and she actually refused to debate about it, saying that I "disgusted" her. That was really surprising. It seemed out of character for her, yet it's perfectly in character for society/people at large. And I wasn't even telling her that the holocaust didn't happen, just that death toll may not have been as high as we think it was.

It was a downright bizarre reaction, and really opened my eyes to the fact that the whole world is under some kind of spell. Consider the fact that in many countries it's illegal to deny that the holocaust happened. If this doesn't sound strange and alarming, it should. To deny freedom of speech over something so particular that's just an opinion about historical facts and not even hate speech.

I would have no opinion about the guy who denies the holocaust happened, I would just have an idle curiosity about whether he's right or not. I wouldn't consider him a racist or anti-Semitic anything because if you really wanted to speak badly about the Jews you'd just call them names or accuse them or something, not flex them in such an indirect and weak way as to deny that millions of them were killed in the holocaust. People are so silly to think that way.