Many who don't see the danger were not here in the 2000's. There are so many great technical achievements that were killed by microsoft, google or facebook EEE'ing the shit out of it. Remember jabber/xmpp? Yeah, both FB and Google implemented the protocol in their chat apps. Everyone was thrilled; I could use my jabber client to connext to fb and talk to my friends. Then they remembered there's not any money in that and killed the projects.

Even if it's good for the fediverse now, as soon as they realize they can make more money by not having to sync with other companies and organizations, they'll be out of here, leaving nothing behind like a swarm of locusts. The only defense is defederation.

if I can communicate with them from my Mastodon account, I would like to have that option.

That's the Embrace part, and it is mutually beneficial. Later on, Threads may give your Mastodon account a special color to mark you as one of the crazy socialists, and let their own users exchange unique awards, super-boosts, or other neat Extended features. Then connection between Threads and Mastodon-at-large becomes unreliable due to technical differences in protocol or just volume of content. Threads users see a handful of their friends drop off for no apparent reason, but 'classic' Mastodon users lose almost everyone and the platform is effectively Extinguished.

I wouldn't call you dumb, but naive yeah. I don't trust anything facebook does and them trying to get involved here is just another shot at unethical data collection. The content on all their sites is shit and sinpleminded so imo nothing they do should be welcome here.