Whilst I can sympathise with the motives of those countries that have made "holocaust denial" a criminal offence, since in the main the topic has been hijacked by nazi sympathisers, and/or racists and obviously some countries would be particularly sensitive to such views, given their own recent history.I remain troubled by the censorship and control that such a law implies however.
Once you start drawing red lines around topics, or issues, and proscribing by law the airing of alternative viewpoints - however wrong-headed and absurd - where do you stop? And who should be responsible for drawing up such limitations? This is why we still have ridiculous, outdated laws such as the blasphemy laws, to protect the tender sensibilities of religious fundamentalists against those devilish cartoonists, or writers or whatever.
So,on balance, repugnant though some of these expressed views are, in countries that hold to the democratic ideal, those that hold extremist views should be allowed to air them, if only so that people can point fingers and laugh at the whackaloons and their prejudices, or their fantastical, unsubstantiated conspiracy theories.