Federation means you can defederate for any reason. It's not a set of principles, it is an ontological arrangement whereby power is distributed. Plenty of users will look for defederated instances to join because keeping facebook out of our shit is what we want. You are free to find instances that are federated. Nobody will stop you.

And as for things they've done, personally I find that knowingly stoking genocide in Myanmar is enough for me to not give them any more chances.