I share your suspicions, Bernard. I think there are some very unsavoury adults piggy-backing on this.
However, as the mother of a child coming up to the teen years, I don't want to throw the whole discussion out.
What I personally am hoping for: keep communication open, explain to DS that he's quite likely to be shown this stuff on his mate's phones or (for all my internet filters etc.) stumble upon it himself (either by accident, or through curiosity, or simply because most teens are very interested in sex - I used to look for the sex scenes in adult library books aged about 14 or so). But that quite a lot of this stuff will be downright nasty - painful, non-consensual (which makes it rape), deeply misogynistic, pushing utterly unreasonable expectations about both bodies and what sex should be like.
And (most importantly) that he has a choice. And that that choice is exercised in a moral context. That he can choose to look at the really nasty stuff, and it will do him no end of psychological damage. Or he can choose not to look at it. And, once he's old enough, look for sexual gratification elsewhere - somewhere where the emphasis is on mutual enjoyment, consent, respect for one's partner, giving one's partner pleasure as well as receiving it.
And I fully expect these conversations to be bloody excruciatingly embarrassing for both parties.
But I'm also aware that (a) I may fail (due to excruciating embarrassment, due to the fact that teens come more or less pre-programmed to ignore their parents on the big stuff) and (b) there are parents out there whose approach is ostrich head in the sand or religiously driven "abstinence only" (which simply doesn't work).
So there is a role for schools. The thing is, you can't discuss this stuff in a moral vacuum. Adults themselves will be somewhere on a spectrum from "look, some sexual acts are abnormal fetishes and probably best avoided, and some - the violent and/or non-consensual ones are flat out wrong" all the way through to the "your kink is not my kink but that's okay" anything goes brigade.
The trouble with the Warwickshire material was not covering this stuff, but that the agenda was so clearly driven by the "anything goes" brigade. Whether because they were just a bit dim but genuinely believed that (some idea that we'd all be happier people if we embraced eating shit for sexual kicks and got in touch with our inner furry), or because they were sleazy perverts actively trying to undermine children's sexual boundaries, I don't actually know.
But sex ed without reference to morality is never going to end well. Because sex is never a morally neutral activity (unlike, say, eating a nutritious meal). It always has an ethical dimension. That needn't be "wait until you're married then do it for procreation in a set of church-approved positions", but it has to, as a bare minimum, include consent, a willingness to aim for mutual pleasure, and a respect and liking for your partner as a fellow human being.