Lots of people who are seeing top-level postings about Hexbear. Net are probably confused about what has been going on and I want to give an SRD-style overview of the whole thing.
Note: As a user of Blahaj.Zone, I am not a neutral party in this and I do not pretend to be. This is how the whole thing has played out from my perspective.

Hexbear. Net is another Lemmy instance that had relatively recently started to federate with Blahaj.Zone and other Lemmy instances. It had previously been known as Chapo.Chat because it began as an instance for fans of the podcast ChapoTrapHouse.
Recently users from Blahaj.Zone (as well as other Lemmy instances) began to complain about the behavior of Hexbear users. The complaints were about rude, obnoxious behavior: Hexbear users calling people "libs" as an insult, denying crimes of Russia and China, denying the crimes of Stalin,...
Such behavior was not necessarily forbidden on Blahaj.Zone, but certain sub-Lemmys had their own rules on these subjects.
One of the threads about Hexbear: https://lemmy.blahaj.zone/post/1854795?scrollToComments=true

After an ever increasing number of users calling for defederating from Hexbear. Net, Ada (admin of Blahaj.Zone) opened a thread to talk about it. The thread was quickly inundated with Hexbear users, complaining in turn about being called out in this way. Though many of their comments exploited a current bug in the Lemmy code which resulted in emoji's being embedded as pictures which results in lots of image spam.
Ada responded by removing top-level comments in the thread which were not from Blahaj.Zone's users, because she wanted to get the feedback of her own community, not from anybody else.
This happened originally in this thread: https://lemmy.blahaj.zone/post/1959801

The discussion on Blahaj.Zone was a back and forth: Lots of people calling for "leftist and queer unity", others complaining about getting harassed by Hexbear users.

Meanwhile, elsewhere: Lemm.ee, a Lemmy instance operated and managed by someone from Estonia, also opened a discussion about Hexbear - at least partially motivated by the admin's increasing unease of the rampant denial of soviet atrocities and the occupation of Estonia by the Soviet Union. Russian propaganda in regards to the war in Ukraine was also an issue.
Lemm.ee was largely encountering similar problems as Blahaj.Zone, though the Lemme.ee admin admitted that the Hexbear admin was generally responsive to reports and complaints.
The thread on Lemm.ee: https://lemm.ee/post/4543536

The thread was also flooded with comments from Hexbear users. The admin of Lemm.ee also responded by hiding most of the comments from Hexbear.
https://mastodon.social/@brooklynman/110911292961470110

Back on Blahaj.Zone, a tangent opens up: A Hexbear user complains about c/196, the new home of Reddit's r/196 which had relocated to Blahaj.Zone and has been its biggest community ever since. The Hexbear user complains about their comments being removed, comments that called out the use of the r-word and other call-outs. The user posts pictures of the removal notices.
Blahaj.Zone's admin Ada steps in and intervenes on behalf of the Hexbear user, having a stern word with the c/196 mod responsible for the removal of the comments.
https://lemmy.blahaj.zone/comment/2136643

A Hexbear admin also gets involved and sends a message to the mods of c/196 demanding the removal of the sub-Lemmy's banner, because it contains "fuck tankies²", arguing that tankies is a slur. The c/196 mod refuses and publishes their message.
[²"Tankies" is a pejorative term for authoritarian socialists in the vein of Stalin and/or Mao.]
https://lemmy.blahaj.zone/post/1961004

While the discussion if Blahaj.Zone should defederate from Hexbear is still ongoing, the Hexbear admins defederated from Blahaj.Zone without warning from their side, because of...

unaddressed ableist removals from the /c/196 moderators, defense of chasers, no-quarter rules regarding our users, leakage of good-faith DMs from our admin team, and a general lack of initiative to punish these behavior

In her a response to these events, Ada points out in a comment that she never had the chance to adress the ableist incident (she was in bed) while other issues had happened in the past and had been adressed at the time. Thus she could not react before Hexbear defederated.
https://lemmy.blahaj.zone/comment/2135406

TL;dr: Blahaj.Zone's users complain about ill behavior of users on Hexbear. Net. A discussion about defederation begins on Blahaj.Zone. Meanwhile Hexbear users complain about Blahaj.Zone in turn and Hexbear. Net defederates instantly and without warning.