From the perspective of racism (which is the context here) it's perfectly valid.
The UN's definition of racial descrimination:
"the term "racial discrimination" shall mean any distinction, exclusion, restriction, or preference based on race, colour, descent, or national or ethnic origin that has the purpose or effect of nullifying or impairing the recognition, enjoyment or exercise, on an equal footing, of human rights and fundamental freedoms in the political, economic, social, cultural or any other field of public life."
I had a colleague who was from the Ukraine, and I once referred to him as Ukrainian, and he stiffly responded, "I am Russian." From that, I assumed that some people consider it an ethnic group independent of the nation.
A lot of people from Eastern Europe are very sensitive about that sort of thing; Russia's domination of the USSR and various brutalities are still fresh in memory, and besides, referring to any Eastern European as a Russian is akin to calling someone from Guatemala as a Mexican. Some people are more sensitive about it than others. (I was born in Russia, and don't particularly care, but I'm aware of other people's sensitivities.)
This happens in other parts of the world, too, of course. I once asked a girl in college if she was from India; she gave me a hateful death stare and coldly declared that she was from Bangladesh.
Which brings up another quirk of humanity, which is we tend to hate the ethnic group that is the most similar to our own. Simply, you hate your neighbor, you don't hate someone on the other side of the world you've never interacted with.
There certainly are many instances of people hating ethnicities very disimilar form them, but that happens after people from different parts of the world migrate close to each other.
Well, sure. Your neighbor is the one who waits an extra week to mow his lawn, which looks bad, and drags down everyone's property values. Your neighbor is the one whose dog pooped in your yard that one time.
I suspect that proximity has a great deal more to do with it than similarity. If your neighbor is actually significantly different than you (ugh, the weird smells from the strange food those people eat!) I would think it makes it even worse.
Russian refers to anything related to Russia, including:
* Russians (russkiye), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries (where they are also known as Ruthenians or by other names)
