If I had to guess, it's because George Soros is often used as synecdoche for "the vast Jewish conspiracy" by anti-Semites, so your comment sounds an awful lot like "the Jews are responsible for ruining Russia".

Which, uh, sounds a lot like anti-Semitic rhetoric not uncommon in, among other places, Russia.

It was flagged for not sufficiently praising the awful behavior of the US during and after the fall of the USSR.