I think the biggest issue they had highlighted (that I witnessed myself, unfortunately) mainly was people with clear bad faith intentions entering beehaw's spaces designated for discussions of and about vulnerable communities and individuals that beehaw wants to make sure to protect as part of their community ethos. Discussions that were calm and respectful and didn't devolve into chaos previously due to the barrier blocks in their community quickly fell apart due to large swaths of users who were able to enter the community without any barriers that would have been stopped quickly if they had tried to sign up to beehaw. Like, a lot of it was really was the lack of post restrictions within their local communities. An example off the top of my head, beehaw requires you to fill out a form to basically make sure you are wanting to join in line with their community policies. For those that get the false impression that they are asking for a large essay or were asking for censorship and get dissuaded because of that, beehaws admin seem to feel that is a good deterrent to those who wouldn't engage in good faith within their community anyway. And it seemed to work on its own, but it quickly fell apart as huge amounts of signups began the surge across the two instances they defederated. Individuals who began to cause problems and enter the communities to troll, were almost all from those instances. It was a matter of they literally can only ban and delete, and with how the modding system in lemmy current system is, it was a losing game of whack a mole they currently cannot win.