they’re making the decision of whom you can & can’t talk to on your behalf
If I want to talk to people on a defederated instance, I can create an account on the defederated instance. Nobody has made any decision for me. You seem unhinged.
whether or not you asked them for it
Admins having the power to decide to defederate is implied simply by being a Lemmy server. It cannot be any other way. The only “asking” that occurs in this situation is a user asking permission to sign up, create an account and use the server where the admins necessarily have that power.