I've never posted in that sub either, but I was banned today, and the only possible explanation is that it was for downvoting. A lot of their posts are self-righteous and needlessly confrontational, so I've downvoted a lot of their memes when they wind up in my feed, but I've never commented on any of them.
This moderator isn't trying to remove hostile comments or stop rule violations; they're trying to artificially lower the number of downvotes their content gets to make the community look less unpopular. You can actually sort posts by recent and see how the percentage of downvotes suddenly dropped off after the ban spree. This is a blatant attempt to manufacture consent for their community by gaming the system.