The publisher using stock images does have the right to transmit those images to visitors. Those visitors don't have the right to incorporate the images into their own public work that they rebroadcast. But Meta isn't asking for that; they want consent from the business to scrape. The subsequent copyright violation is then a matter between Meta and the vendor of the stock images.
Imagine someone asks you: see that guy across the street? Do I have your consent to search his pockets? If you say yes, what does it mean? Precisely nothing.
Suppose you are asked: do I have your consent to search the pockets of everyone in this neighborhood? If you say yes, it still means nothing with regard to the guy across the street, who has not given any constent, but you've consented to your pockets being searched.
I think if you have some kind of authority over the place where this happens and/or if you facilitate an illegal action then you could be breaking the law.
If you signed some agreement whereby you pledge to protect licensed images from AI scraping bots, then signing off on a consent to Meta would breach that agreement.
There is no such agreement. Licensees of images are understood to be broadcasting them to the entire world, including anonymous visitors.