So - radical feminism doesn't mean "extreme" feminism, or "man-hating" feminism, it actually means radical in the sense of "getting to the root of."
So the interesting question for a radical feminist to ask IMO is not "are there some individuals who like this and is it okay - their kink may not be my kink but that's okay?" (which is presumably how a liberal feminist would frame it).
A radical feminist (I'm probably on the fringe of being a radical feminist) would ask "why in social terms is BDSM popular, is it freely chosen or is it pushed on women by social expectations, why does the gender balance seem to have changed (as someone pointed out upthread from men being on the receiving end to women being on the receiving end), why has it become normalised, why does it overlap with general violence against women to such an extent?"
Take choking. Back when I was young, "erotic autoasphyxiation" was something men did largely to themselves. And there was a class element - I remember joking to a friend "Why is it when you see the Sport headline MP found hanged in basque and suspenders you just know it's going to be a Tory MP?" It was also a practice considered extreme even by my friends who were into BDSM, because it's a practice which cannot be done safely.
But now it seems to have become part of the normal repertoire of heterosexual sex - and I've read lots of posts on dating threads here about women finding first time they DTD with a new partner, he strangled them without discussing or asking first.
A radical feminist would place this within the context of ever more extreme, misogynistic porn, and a general backlash against feminism in particular and women in general. Why is it being done by men to women, as an almost expected act, often without bothering to ask first? What role does porn and/or erotic literature like 50 Shades play in persuading women that it's something they should like or at least should be prepared to try? How much of them engaging in the practice is because it really does it for them, and how much of it is because they think it's what you do to demonstrate to the man in your life that you're up for it and not some sort of prude?
To an individual woman who said "but I like it..." I'd say "(a) What aspect of it and (b) Why?"
If the answer to "what" is "the head rush" for fuck's sake just buy yourself some poppers - it's safer.
Re. the answer to "why" my own hunch is it's a form of society-wide Stockholm syndrome. We as a sex know we're massively vulnerable to male sexual violence, so we (collective we - not all of us obviously but a substantial subsection) collude in the eroticisation of female submission in order to turn the reality into a (twisted) fairy-tale version we can live with. I would advise any woman who says she likes choking to really sit down and (a) do the Freedom Programme to make sure she can tell the difference between BDSM and abuse and (b) have a long think about why submission fantasies do it for her, and whether there are any other fantasies she could engage in instead.