Auto-block federation from servers that don't respect.
NO! Do NOT defederate due to how an instance chooses to operate internally. It is not your concern. You should only defederate if this instance causes you repeated trouble offenses. Do not issue pre-emprive blanket blocks.
Do not make assumptions on how other instances are operating. You don't know what measures they're taking. If they did not cause you trouble yet, don't try to predict it by making generalizations. It creates an echo chamber Internet.
Agree! Defederation is a nuclear option. The more we do it, the more we reduce the value of "the fediverse", and the more likely we are to kill this whole project.
I think defederation should only be a consideration if an instance is consistently, frequently becoming a problem for your instance over a large period of time. It's not a pre-emptive action.