I am probably going to personally block Threads for myself, but IMO I don't really think that defederating is the right way to go for this instance. I think it's nice to have a place where I can get everything so I get to choose what to see. I'm not sure about elsewhere, but I really want to be able to see whatever is out there. IMO it would be a much more radical statement if a majority of Fediverse users (as opposed to a majority of instances, which is only reflective of those users privileged enough to run an instance) blocked Threads from their feeds.