(Note that without a critical failure of theory of mind, a retort that the Russian charges against Ukraine are obviously false while the American charges against ISIS are obviously true is not meaningful. Can you say with confidence that growing up in Russia, you wouldn't have the same certainty that the Russian narrative is basically correct while the Americans are spouting self-serving propaganda? Is there some way you can imagine yourself convincing a Russian that American media is to be trusted without making your proposed chain of trust circular?)
Just because "cultural genocide" and "slavery" are both bad things does not mean they are on the same scale.
Also, to put it mildly "cultural genocide" is not applicable to the situation for multiple reasons.