these platforms have the know how to deal with spam and they will be incentivised to share that tech with other federated instances.
Based on what? These private companies aren’t going to share anything because they owe it to their shareholders not to.
I dont think any of your points are wrong, it’s just the association with Facebook people are anti. The fediverse has a great reputation for being completely removed from profit motive driven mega corporations. Facebook joining is gonna make people question the fediverse is my understanding.