If the instances that want to be a safe space defederate from instances espousing an ideology they can't stand, I don't see the problem. If an LGBTQIA+ instance and a Salafi Muslim instance defederate each other, most of their members are going to be happier even though it might be hard on gay Salafis.
"This generalist instance I am on shouldn't tolerate Salafis and I demand we defederate the Salafi instance tomorrow" sounds the same in outline, but feels very different. It's closer to an attempt to push your enemies out of the public square than an attempt to prevent harassment of your private meeting.