The protest, in which three people placed themselves in containers resembling supermarket meat trays, was meant to compare eating meat with cannibalism.
So this is where the thought pattern of "we are the same as animals" leads to. It makes no sense, but whatever. We were obviously made to eat meat, and we not really made to drink other animals milk. But for some reason these people think it is wrong to eat meat, while drinking milk is probably bad in their minds, but not as bad as eating the cow.