I specifically choose instances based on their instance block list. If they block a lot of instances, I don't consider them. My ideal ones are the ones that are a bit free and yet are well connected, but sometimes well connected means "allied to the mass defederators" because people in general become super compliant in the face of isolation.

Sh.itjust.works may start banning communities to regain federation to Beehaw, and then Beehaw will ask that sh.itjust.works defederate a "wrong" instance or two, and by the time we know it, we'll all be banning the same instances, and we'll be a cute little echo chamber of "tolerance".

By that same measure, I usually avoid any instance of community that claims to be a "safe place". They're the likeliest to always be attacking others because that's how you stay safe, through unending violence.