Many people have a preference for civility politics. They prefer negative peace over a positive justice. They have similar reactions when vegan animal rights activists point out things that trigger their cognitive dissonance.
Thankfully, their pissing and moaning about these groups still bring more attention to these urgent issues than quietly begging for justice ever has, so even if they don't like it, these kinds of stunts are still effective.
Understandable. But yeah, unfortunately, activists will likely need to continue doing more outrageous things as time goes on and these issues continue to be unaddressed.
And if it makes you feel better, those paintings are kept in protective frames, so the art itself has never been damaged to my knowledge. Even still, I'd take a few damaged works of art over an even more irreparably damaged climate.