I very much liked the 'dark' opening. It began with gleeful discomfort in the exagerrated portrayal of the animation assembly-line, then went gingerly onward into fantastically macabre absurdity. If the episode that it preceded had possessed some aspect of that, I might have watched it. I admit, I'm literally unable to comprehend how some people might find it really upsetting. It's the emotional equivalent of somebody speaking Mongolian at me. I recognize generally what it is, but it means nothing to me.
I particularly don't consider it to have been, "mean-spirited." Family Guy's routine belittling of the physical appearances of particular people strikes me as mean-spirited, but not this.
The reaction to it as 'satire' seems misguided. Several people seem to be making a very straightforward assumption that it is meant to satire real conditions, especially those of the poor Unicorns who are senselessly exploited to punch holes in discs, but I think that it could be regarded as instead as deliberately preposteous exagerration to the end of satirizing beliefs held about the manufacturing of The Simpsons as associated media.
Perhaps it's not even anything that specific, but just a strange, grim sequence that can be appreciated on its own that borrows from subjects for satire merely as a convenient context for black comedy.
. He courted Bansky to work on the show.
