The united states was founded on freedom of speech period including freedom to worship Jesus without tyranny of the pope of Rome. Freedom of speech is fundamental in any free society. When the pilgrims came here in 1620 with their Geneva bibles, they were escaping persecution from the RCC. Freedom of speech allows us to not only hold our opinions but is also important in matters of personal faith and how that person expresses it.
Although Holocaust denial should be discouraged, it should never be made illegal, because one of the basic tenets of American democracy is to allow people to think however they want to without censorship or persecution. Holocaust denial is a terrible ideology, but if we made it a criminal offense, this would be considered unconstitutional and a violation of American principles.
The most important point here is the classic point that freedom of speech means defending the right of others to say things that you may hate or dislike. Holocaust denial, while incredibly, shockingly incorrect and contrary to so much material evidence, is still speech that must be protected if we're still to have free speech.
While it should theoretically be a crime to say something that hurts so many people and is so blatantly untrue, it does not seem as if any opinion held by a person or a group could be a crime. To say the Holocaust never happened is to hold a misguided opinion.
Holocaust denial isn't a crime in the United States so long as it doesn't impede the rights of other people. Everyone has the right to an opinion, even if it is the wrong one. Holocaust denial isn't a crime in the United States because it is protected free speech under the First Amendment.
No Holocaust denial should not be a crime in the United States, because our First Amendment rights trump all. Even though someone might say something that is very hurtful, as long as they don't threaten violence, they are allowed to say it. People are allowed to state things that are wrong if they want to.