How disappointing: I have always liked Emma Thompson, who strikes me as an intelligent, thoughtful woman, despite – or rather because of – her propensity for offering controversial opinions that cheerfully dispense with received wisdom. But her recent remarks about "cougars", the name given by the media to women who have the temerity to date or even marry younger men, seem heedlessly to accept the sexist terms of the conversation. "I don't get it. It seems predatory and I don't really approve," Thompson reportedly said. "It is easy to be flattered, but I am no cougar."

Assuming the report is accurate, there is one thing about which Thompson is right: she doesn't get it. A woman who is called a cougar seems "predatory" for a reason, but it is not because she is dating younger men: it is because she has been given the name of a predator. This is why it should not be "easy to be flattered" – it should be easy to be insulted.

My thesaurus offers the following synonyms for "predator": bloodsucker, leech, vampire, harpy, vulture. Isn't it coincidental how many of these names are traditionally used to denigrate women?

But it doesn't take a thesaurus to think through the reasons for objecting to a sexist and derogatory term. The problem isn't simply that cougars are predatory animals, it is that the label exists in the first place. They could be called "platypuses" and I would still object to the implication that women dating younger men are such anomalous beings that they require not just a new name, but a new taxonomy: along with cougars we now have pumas and, evidently, cubs. Men who date younger women have their own familiar label, to be sure: we refer to them as men. Men do not get called jaguars, they only drive them. Welcome to the double standard: it is alive and kicking the woman next to you.

By no coincidence there has been a marked resurgence in animalistic nicknames for women more generally: those absurd "mama grizzlies" who were all over the US midterms leap to mind, as does Sarah Palin's even more bizarre invocation of "pink elephants" – a reference presumably meant to suggest a feminine version of the Grand Old Party's traditional mascot, but which unfortunately also suggests that female Republican candidates are the drunken hallucinations of a populace afflicted with delirium tremens (which might be the only explanation for Christine O'Donnell's candidacy).

What is even more unfortunate is that these are labels that women are embracing, bestowing upon each other with pride – or, in the case of Thompson, evidently thinking they ought to find flattering. But they are not flattering, and they are not empowering. There is a long genealogy of bestial nicknames uniquely bestowed upon women, of which cougars, pumas, and – God help us – "mamma grizzlies" are just the latest.

Women who are sexually attractive have always been compared to cats (or foxes, or even beavers). Cougars and pumas are just updated versions of an old phylogeny that begins with kittens and pussies. If women are unattractive, they are cows, heifers, sows, vixens, shrews, dogs, or bitches.

Given the reactionary sexual politics of Sarah Palin and her followers, including Sharron Angle's advice to pregnant victims of incestuous rape to "make lemonade out of lemons" by bearing unwanted babies, their regressive discourse doesn't surprise me.

But I would have hoped that educated, intelligent women like Emma Thompson would be able to distinguish between objecting to an objectionable label, and objecting to the women who are being demeaned by it – and thus demeaning us all.

Sarah Churchwell is senior lecturer in American literature and culture at the University of East Anglia