I think most people simply just don't know how federation works and they imagine that defederating blocks Facebook from accessing your content when in reality it's the exact opposite; it places one way mirror between us from which only they can see thru. There's also some great irony in the fact that they're talking about genocide while advocating for using the nuclear option to block Facebook despite the massive number of innocent casualties it'll cause.
EDIT: Turns out I was mistaken. Defederation indeed does stop the flow of data both ways.