David Irving is a great example of a bad historian, somebody that lets there personal bias rather then evidence, control what goes into their books. But to say that he should be jailed for being a Holocaust denier is equivlent to saying that people should be jailed for writing books that take a non-government approved posistions on history.
I understand that cases like this can be complex, because many people will carefully skirt the line on how far they can go without directly advocating violence. But nothing I have seen says that Irving is in that category.
On a side note, I don't think the European countries understand the degree to which these laws make the various forms of neonazism and fascism popular. Not only does making it illegal create a black market for nazi goods, but when any government tries to make an idea illegal they just encourage some people to embrace it.
Jay