By continuing to interact with Thread users you’re enabling those users to feel justified in not wanting to leave.
People do not have to leave Threads. They should, but they don't have to. No harm in interacting with them. In fact, such interaction will make them aware of the alternatives.
That won't happen to Fediverse because nobody here is willing to be 'captured' and 'destroyed'. We don't give a fuck if Threads wants to break its own protocol.