Anon is retarded and got hit with the other filter. Onions = soi (as in soi beans, soi milk), basedboy = soiboy.
The election got a lot of reddit kids who wanted to be epic 4chan hackers riding the Trump train sincerely (and becoming a large minority or even majority on /pol/) rather than just wanting to watch a bold retard BTFO Shillary, and began embarrassing themselves wherever they went. Far leftists latched onto this and began caricaturing anyone opposed to them as a retarded 14-year-old redditor ("gamers rise up" and "own the libs" are a couple of their favorites). Their Joker memes gained some traction and now they're breeding their own leftist version of the retarded 14-year-old to "own the nazis."
It's jarring to see on 4chan, since /pol/posting is seen as a given, often hard to distinguish from edgy bantz and is generally ignored, since it only ever manifests here and as the odd ebin trolling on social media, whereas leftist ideologies have been a cancer shitting up all entertainment media and the arts for the better part of a decade now. The fact that you see those kind of posters here of all places is a combination of contrarianism to neo-/pol/ posting their shit in every board and 4chan becoming ever more mainstream/targeted by ideological groups hostile to the culture. They're just a symptom of more and more newfags flooding in who refuse to lurk or assimilate and slowly dilute culture with their growing demographic (high traffic boards like /v/ will often have enough newfags in a thread to shout down culture enforcement, as opposed to the old state where a majority of acclimated users would bully newfags into lurking if they started acting too retarded).