Not sure, wouldn't that be the same as willing uncorked actors simulating murder on screen, in some ways? Maybe not, as the key thing in censorship is whether the watcher is meant to abhor it or get turned on, that is why Human Centipede 2 got banned, I think.
Of course, going back to the OP's post, well, national treasures Caitlin Moran and Victoria Coren have fessed up quite cheerfully to watching porn, with nary a blush, so she's hardly alone. I mean, Coren has even made a porn movie and written a book about it. Still, they're women, so it's okay, and Coren sounds posh, and posh gals banging on about sex always puts them at a premium.
Not sure if Lucy Mangan watches porn, one senses that for her, 50 Shades of Grey on Kindle would be the worst kind of atrocity imaginable...
Blokes can fess up to watching porn so long as a) They look like they're getting sex anyway and b) they are charismatic comedians who can pass it off as a joke, or somehow ironic, or fessing up to their vulnerabilities and pratfalls e.g. Frank Skinner and Russell Brand.