I'm not in favour of pre-emptive defederating. It feels like censorship doing so and that bothers me.
Their note to their users specifically says to keep their anti establishment opinions and trolling to their own communities and don't spread it further for fear of defederation. It hardly sounds threatening to us.
Defederating can happen at any point, and I think would be better kept as a reactive response and last resort rather than proactive.
The more our large instances start fracturing and closing off from one another the less useful Lemmy will become. You're hardly blocking out an idealogy, if hexbear users wanted in they could just sign up and that would make it harder to find them. At least having them federated makes it easy to filter out @hexbear if we wanted.
Practicing tolerance goes both ways. Calling communities 'them' vs 'us' and judging a group based on the noise of the few doesn't seem like the right approach. If hexbear became a problem and moderators complained of hate speech and conflict then absolutely we use the tools we have to keep things functioning, but filtering out groups because we don't like 'their' belief systems will make us judgemental and biased as a result. This is a platform to promote discussion not an echo chamber to gather like minded opinions and bounce them off each other in perpetuity.