It has to do with overreaching definitions of colonialism, imperialism, etc, in part thinly veiled hate for durianrider and freelee too. some of these people just look for fights, its youtube. if Chiang Mai were a tiny village and white vegans were their first contact with white people, then they might have a legitimate concern, maybe, but its been a tourist destination for a long time and vegans are still only a very small % of the tourism there.
I had someone tell me we should protest some things they disagreed with, but prisons full of tourists really wouldn't be helping anything. That is putting western morality on a culture that isn't yours, basically doing that imperialistic thing they were supposed to be against. .