It's clearly meant as a joke but give the spate of acid attacks that have happened in the not too distant past it's a very poor choice, especially from an ex-nurse. I doubt she'd find it funny if someone jokingly said the same about a left wing liberal or a feminist.
There does seem to be a bit of bias in favour of left wing in terms of jokes which could, but probably shouldn't, be considered as inciting violence or hate crimes. I think part of that can often be the tone in which they're said, but also I think in terms of the opinion of those incharge on those who hold right and left wing views. They seem to be that 'left wing can tell it's a joke and so won't act on it. some right wingers can't and will act on it', which is completely wrong and patronising.
There is also a definite bias in terms of what women and minorities can say. They can make all sort of stereotypical crap about men or white people and it's fine because it's a joke but the other way round it's not fine, even though it's a joke because it's sexist or racist.