> Do we really need tens of thousands, or even millions of porn actors?

Who do you mean by "we"? I guess if these people are able to earn a living then there must be a market for their content and the answer is yes.

> wouldn't society be better off if they did practically anything else as an honest living?

They make content that others are willing to pay for, with little to no negative externalities. I can't see how that's bad or dishonest?

I don't see why you're criticizing pornography when there are lots of jobs out there that are actually dishonest and are net negatives for society at large, like the aforementioned religious lobbying group the article is talking about.