I disagree with the reason it was unfeatured.. I don't think memes should be disqualified solely on their political or ideological alignment. However, those ... *checks notes* ....
"PoliticsTOO announces itself as a forum for liberals and moderates. We have no obligation to platform the same kinds of right-wing memes that are ever-present on the top page of politics and similar political streams of a conservative bent. We have as much of a right to ban right-wing memes as the mods of a stream for dogs have the right to ban cat memes. This rule preserves the essential character of PoliticsTOO as the principal place on Imgflip where liberal and moderate memes can be reliably seen and heard. At the same time, we do not aim to be a total echo-chamber. We recognize the value of hearing and responding to different viewpoints. Ergo, conservative commentary that is logical, respectful, and informed is permitted in the comments sections."
... are the rules. I haven't been very active as I've been fulfilling my obligations on the domestic scene... If you're looking for non-extremism, I wouldn't recommend imgflip for any alignment. This is the place where online activism can be at its most heated.
I suspect, given the context of the letter, that you're basing your view entirely on your exposure here where anonymity is the name of the game and someone could be pretending to be what you suggest and sabotaging your experience. I would encourage you, in your endeavors, to seek other "liberals" or "progressives" (as I am unsure under what context you're using these labels, specifically) who might broaden your horizons.
It's unfortunate you feel this way, and I wish you the best of luck in defining your political alignment. I hope,, for your sake, you'll one day see the political spectrum as so much more than a LvR or DvR. Republicans have Liberal tendencies too, they just don't want to admit it for the namesake. (In my experience.)