Post-war Germany was so afraid of itself that they needed  to outlaw Nazi propaganda, Holocaust denial and the like. Ataturk's refounding of Turkey was not such a clean break from the Ottomans.

Blair is now getting ready to crack down on "offensive speech" and "enocuragement of terrorism" in hair-raising ways.

A society committed to the notion that government is always bad will have bad government. And it doesn't have to be that way. — Paul Krugman

Can someone explain to me why this is different in principle?

If you're talking about freedom of speech as an absolute, the way us Americans see it, no difference in principle. That's why the ACLU routinely goes to court to defend white supremacists.

However, postwar Europe adopted the principle that certain ideas are dangerous, that there is a rather substantial difference between racism and anti-racism and the former should be a crime.

Personally I prefer the former, but few Europeans seem to agree with me.

I don't think its good at all.  Unfortunately, I don't get to vote in Germany.

Idiot/Savant
No Right Turn - New Zealand's liberal blog

I missed this thread, but to me it's quite simple:

• in one case, you promote ideas that have led to genocide in the past. The reasoning is that you are a potential threat for going down a known dangerous path

• in the other, you are being prevented from talking about history. You can be a threat, but not to a democratic regime.

I understand the US First amendment logic and am glad it exists, but I cannot blame the European countries, with their history, for choosing this path. Note that France has a similar law against négationnisme.

In the long run, we're all dead. John Maynard Keynes

And some of them mentioned in the comments above.

1) It happened in Germany despite a democratic constitution (Weimar Republic) so we Germans probably feel that we shouldn´t tolerate such speech again.

Simply said, the first German republic failed after only 15 years. We didn´t want it to happen again, so....
It´s a bit different with the USA. After more than 200 years living in a republic, Americans probably feel more confident about their constitution. :)
Although I agree that laws and regulations in Germany should be relaxed now. More than 50 years after the "second" republic was founded.

2) Public relations.
It´s one thing to publish Holocaust-denying stuff in Canada, the USA or Denmark. Or hold speeches glorifying Hitler and the Nazis. Free speech there. It probably would be quite another thing if such stuff would happen in Germany.
Can you imagine the worldwide media coverage if such things would be published in Germany?
I can just imagine the headlines in Great Britain or the USA! :)

Simply said, stuff happening in the USA or Canada that would be ignored by the media, would be headline news if it would happen in Germany.