Additionally, you think Americans 'would never do such a thing'? I don't know how you can argue against denial laws in the US and for them in Germany.
People in general have always had flaws that result in them committing horrible deeds. The holocaust occurred because many individuals committed acts that they were able to rationalize to themselves - which as a whole resulted in a great evil. No law about what people can say in public will prevent such an event.
You can't stop Holocaust denial with a law. You just drive it underground. Worse yet you give Holocaust deniers a valid recruitment argument in that they can say the government is "trying to silence them" which makes their beliefs seem more plausible than they are.
The best thing to do with Holocaust deniers, or any other foolish movement for that matter, is to let them speak their mind and make fools of themselves.
Some things should have to be underground, which many will see as a mark of shame for it. Most people don't want to be underground. You seem to take "opposed by the Government" as a badge of honor, which is understandable, but it is not how a majority of people think, especially outside the US.
That's where the flaw is. The governments of these other countries think they can suppress belief simply by suppressing speech and they can't.
In some countries, e.g. Germany, it's a lingering part of world war 2 which is not yet obsolete. It's a war act, and it's suppressing a genuine, serious risk of violence.
I know that's a bit hard to believe for an American who would never do such a thing. The holocaust was hard to believe too. We should not ask or encourage Germany to repeal their holocaust denial laws before Germans judge that they are ready.