It’s not just a matter of blocking Threads users.
Facebook is coming on here to slurp up data I don’t want them to have, and enriching their own Threads ecosystem with Fediverse content they haven’t lifted a finger to create.
Not to mention, when Threads users are able to fully interact in the Fediverse, do you really want that particular bunch to create noise in your communities? I don’t. There’s a reason why I avoid Facebook in all its forms.
I would cancel and tell the restaurant why.
Businesses need to know why they lose customers, because if enough of them report the same reason, they might do something about it.