I am not a fan of PornHub because I feel that many of their practices are unethical. That said, as with so many other controversial topics, keeping things legal is ultimately better as it provides opportunities for oversight and regulation. Things being legal don't make them okay though, I am in favor of legalizing prostitution but I also believe it should not exist in the first place.

Kristof's piece is a classic "moral panic" article. It could have been written basically at any time in the last 100 years (at least). What is different this time is that the focus is on a modern delivery medium, the internet. But scandalized reporting about the wide distribution and availability of child pornography is nothing new. I remember being a kid and seeing headlines in the newspaper about "internet pedophile porn web rings" being taken in by the police, that was in the 1990s.

As for the motivations behind the people pushing the narrative, they're diverse. Some are religious, some are political, some have nefarious motives. Ultimately these things always distract from the thing no-one ever wants to do: hear from the victims and find real ways to prevent the abuse.