Ukrainian nationalism has been a "thing" since at least WWII. The partisan fighters of WWII continued it as a movement after the war's end. Russian nationals were sometimes denied employment, housing, and otherwise harassed inside of the Ukraine throughout soviet times. I've heard accounts of (pretty serious) ethnic discrimination firsthand from Russians who lived in the UA, it's not something the west just made up on the fly after the cold war ended.
Exactly how widespread it was I don't know, but the conflict's been around a lot longer than the digital age. Russian nationalists tend to think Ukrainians don't exist (when they're not calling them hohols) while many Ukrainians insist that they're a separate group. The truth is somewhere in the middle (there are minor ethnic differences) but it's not all just a western fantasy.