Well, it's true that somebody has done it. Those who've done it are either exiled, behind bars, facing suspiciously timed "unrelated" charges that could result in extradition, or anonymous. Not sure that invalidates the point the person you're quoting was making: that there is repression of dangerous ideas in the US.

I'm less familiar with Germany, but I'm willing to bet that while people in principle can say whatever they want (with some exceptions), there are other, less visible forms of repression and/or means of neutralizing those opinions. That they are less overt than in China doesn't mean they are not there.