Most of the top comments are "this is a terrible idea and here are the reasons we should never do it", and his comment is "we can do it sooner than you think, here's how". To people concerned about censorship and creation of echo-chambers, the trollface image is adding insult to injury for those harmed by the filter as well as being an easy-to-imagine detail so people are less detached and more emotional in responding to it.

Also personally, while I grudgingly accept that people currently use "troll" to simply mean "mean person on the internet" without regard to the more specific meaning that "troll" used to have, I'm pretty sure the trollface is specific to trolling in the latter sense, while it's only the former that could plausibly be detected by a filter, and the incorrect usage of the meme aggravates me no end.