The idea is people who point out a movie like Pearl Harbor is inaccurate aren't attacked in the US.
Meanwhile in the U.S. you can very well be sued into submission and silence if your opponent is sufficiently deep-pocketed. Not exactly congruent to top-down repression of unruly bloggers as happens occasionally in Russia. But still, we in the U.S. aren't always as free to "tell truth to power" as we might like to think we are.
https://en.wikipedia.org/wiki/Strategic_lawsuit_against_publ...
What triggers them is any suggestion that the Nazis were good and suggesting the surrender of St Petersburg to the Nazis would have been great definitely falls into that category for the majority of Russians.
On top of that St Petersburg really has a problem with violent Neo Nazis groups, or at least had - don't know how it's today.
I'm actually pro freedom of speech to a degree that most people in Europe are not (I would allow them have their stupid demonstrations) but the truth is that in most countries some ideologies are forbidden. Nazism is forbidden in most parts of Europe or how about showing public support for ISIS.
I'm 100% sure it is forbidden everywhere in Europe (maybe with UK being the only exception).
Well, it's not like anyone's trying to get the USSR officially reconstituted. But there does seem to be a very deep undercurrent of respect about what the USSR stood for (as a form a "Greater Russia", in effect), independent of the CPSU's hegemony over it.
As exemplified by, for example, Putin's famous statement about its collapse being "the greatest geopolitical catastrophe of the century". And the widespread contempt for Gorbachev for having presided over it (or at least for having caved into under far too generous terms for Russia's geopolitical adversaries).