Given the wording, I still don't see how this works. A more long term, indirect approach would probably work better.

If Facebook had a continuous, long term, PR campaign, where they reasonably established themselves as helping small businesses, and then they did this. I would get it.

But like this? In isolation, it feels more like a knee jerk reaction and not a thought out messaging campaign.

My guess is that the root cause is one of internal perception vs external perception. They see the threat and honestly believe they're in the right. That's how they rationalize it, but the rest of the world assumes more nefarious intent (which is also exaggerated, the truth is likely somewhere in the middle).

The small business stuff is just rationale for the rubes. It is a stalking-horse argument for their real interests.

And I'm not sure what unfair 'nefarious intent' people are assigning - FB have made it clear that one of their goals is reducing Apple's control over their own platform.