I guess that is a viewpoint, but to be fair, there was child pornography, some rape shit (like actual stuff), and some other shit on the website. This doesn't really stop it considering that other porn websites exist, but still--
At another note, pornhub does not have the ability to manually go through every video, that would take too long to be feasible. They also don't have an infrastructure (... pretty sure? imo? MoistCritikal's "The Official Podcast" talks about this sort of thing), so software built into the website to detect such things ain't gonna work (although how one would go about that I would not know at the slightest).
Personal opinion? They should've gotten some volunteers or somethin, but they were at knives end from mastercard and visa or some shit, so that would've taken too long. Nevertheless, volunteers themselves might of not worked out as well as I think it would in my head, what do I know about well: cleansing video websites from TOS.