Earlier quoted context omitted.
A good chunk of that anger was because of trolls. People extending someone else's flag over other's artwork, random streamers calling their followers for vandalism, and general griefing. Since regular users are limited to one pixel every five minutes, it can be exasperating to see their effort erased in a few seconds.
You might be missing the point of those who disagree with your take, which is to call those who want to do different things on /r/Place than you 'trolls' or 'griefers' is itself just you projecting your own value judgment onto them, or acting as if you are the judge of what is right and wrong. From the perspective of someone who likes /r/theblackvoid, the pixel artists coloring over the void are just trolls and grief…
I'd go as far as to qualify people who practiced r/TheBlackVoid in the canvas as antisocial, since filling a single-color void requires very little cooperation between themselves.