The point of federation is to not have a single central point that controls instances. Instances are automatically federated with all other instances, generally. Its up to a given instance owner to decide to defederate from another instance. And thats the “nuclear option”. Ive only seen it done when the instance is posting hatespeech/CSAM/etc.
You can request it to the admins whatever your home instance is but I doubt anything would happen.
Block it in your client, like you have suggested.
A third option is to host your own instance, which will give you control over what other instances you federate with