In my opinion there is something wrong about the definition of "holocaust denial".
The term suggests that a "holocaust denier" completely denies that the holocaust even occured. The official definition however is going far beyond that: It's already considered "Holocaust denial" if someone only questions the official number of 6 million jews killed, or if someone says the holocaust wasn't that unique because there were similar mass murderings in history.
In my country (germany) that's the definition of "holocaust denial" and you can go to jail for several years for "holocaust denial". I think such laws are bad and in fact counterproductive, because if people cannot legally express their doubts about the official version, you cannot explain them and it only leads to conspiracy theories etc. For example, I can understand that some people think that the total number of jews killed by the Nazis may actually have been quite a bit lower than the official number:
The official number of jews killed has always been 6 million. And up until the mid-80s, the official number of people killed in Auschwitz was 4.3 million. (I remember that still in 1992 when I was visiting a concentration camp with my school class we were told that number). Nowadays however it is proven that the number of people killed in Auschwitz was only about 1.2 million. So I can understand that some people may think "Wait a minute - if the number of people killed in Auschwitz was overestimated by 3 millions for decades, wouldn't that mean that the total number of jews killed was overestimated as well?" There was never any public debate about this (at least in my country), probably because questioning the official number alone could lead to going to jail. It was never publically explained as well, in fact I think only few people even know that the number of people killed in Auschwitz was overestimated for decades. That makes perfect breeding ground for conspiracy theories...