If you are A/B testing your users to get past their defenses, you should be at least somewhat responsible for not selling them total bullshit.
That's what doctors are for...
Illegal to advertise any prescription meds where I come from, let alone quack cures for cancer.
I was absolutely shocked the first time I visited USA and saw tv ads for heart medication... Could not wrap my head around it ...
The First Amendment means that there has to be extraordinary proof of direct and immediate harm before the government will step in and stop speech. Note I'm referring to the the prescription drug ads (which actually are pity heavily regulated - they have to be very careful what they claim), not the quack cures. The quack stuff is typically illegal as it's being described in TFA, but it's international, and the FDA/FTC would have trouble enforcing an action against a Mexican hospital.
Just like untested treatments can be. Advertising medications and treatments should be entirely illegal. Full stop.
Signed, Some pharmacologist
I think FB can do the same. Yes, it would add overhead and time delays and it will cost more, but I think it's worth having reviewers before ads get pushed to users.