One can not make that argument at all about a man born in Ukraine who specifically called himself Ukranian.
I think Malevich participated in the cultural life of Russia (even if he wasn’t Russian). At the same time he can belong to Ukranian and Polish cultures too. Nikolai Gogol is one more great person who unites Ukranian and Russian cultures. It is natural that people of different nationalities can live in one country, it is natural that even greatparents of one person can belong to different nations.
I think trying to break such connections is as senseless as trying to stop rivers.
It is natural that life unites people of different nations.