doesn’t mean we have to hand it to them on a silverplatter and allow them to scrape it legally

They could have just set up a simple Pleroma on Raspberry Pi and it would have been just as "legal" as any other instance. You'd need to turn on AUTHORIZED_FETCH and set up authentication on the Mastodon API, otherwise everything is public and unauthenticated (even if the instance is suspended/defederated).

But if enough instances say no, that means they are not welcome. Democracy and all

mastodon.social has already said yes. So have all the other big instances. Most of them have said "we'll wait and see". So democracy served I guess

And the last point is the dumbest: Threads will just include a revenue sharing model like Youtube does

Yeah, maybe. Who knows. I'll deal with it when it happens rather than knee-jerk years in advance. Threads has a long way to go, it's missing a lot of features to put it on par with their other commercial competitors, so I think they're going to be busy doing other things.