The whole problem has in fact strong connections with linguistics. English term "Soviet" can be used both as noun and adjective. In Slavic languages these are two different words. There is a Russian adjective meaning "Soviet", which was widely used (as in examples I've showed above), but a noun has never been created (hence: Soviet man, also Soviet nation etc.). As an English language allows for that, you can use term "Soviet" as noun, but only when it corresponds with intentions of person speaking.