I'm not trying to defend any of this person's arguments, but "art is imperialist" weirdly has something to it.
Empires love art. I mean i do too, don't get me wrong. But brutal imperialist regimes are tied to a lot of artistic flourishings. It's mentioned in The Dawn of Everything as a really common historical pattern which hasn't had much good scholarly work.
The musician and political scientist John Maus also talks about how music always reflects elite power structures - under capitalism music is a commodity, earlier it was to glorify god and the church, etc.
I think you can't study history without realising that there is some kind of connection between imperialism and art.