There's at least two groups of people who potentially stand to lose from widespread discussion of PUA

I can assure you that there are plenty of reasons to find PUA objectionable that don't fall into either of these two categories. In general, just the arms race, negative-sum-gameness of it. Also, there's the fact that a lot of what is passed off as PUA wisdom is just plain wrong, which is certainly good reason to dislike it on purely that-which-can-be-destroyed-by-the-truth grounds.