The real problem is what comes AFTER.
After these holocaust deniers nuts ... who else is going to be put in jail?
I'm thinking about accusations of 'xenophobia' or 'islamophobia', for example.
A political culture that is in denial about a serious social problem will condemn those who seek to discuss it, and try its best to silence them. For a long time now the European political class has been in denial about the problems posed by the large-scale immigration of people who do not enter into the European way of life. It has turned angrily on those who have warned against the disruption that might follow, or who have affirmed the right of indigenous communities to refuse admission to people who cannot or will not assimilate. And one of the weapons that the élite has used, in order to ensure that it is never troubled by the truths that it denies, is to accuse those who wish to discuss the problem of ‘racism and xenophobia’. That is the problem.
You mention Islam. We are all aware that some adherents to that religion commit murder and suicide because of things written by their prophet. Would you defend his writing as the exercise of free speech?