This is nothing more than baseless speculation on the part of the author, unless he/she has statistical evidence that shows a marked increase in adultery after the Internet became readily available to most Americans.
I think this article is bs. While I don't fault the author for the intention, I doubt adultery is all that prevalent. And I don't think internet porn is leading to adultery, in fact I would argue that internet porn prevents adultery---a guy can spank the monkey in front of the computer---and never have to cheat on his wife.