Crikey.
Was that on here or elsewhere? I'm Christian and I think Christianity in the UK is about culture. 
The skirt size thing does sound a bit poor - it's not possible it's just brands being useless? I've got (adult) clothes that are different sizes from the same maker.
Anyway, about rationality. I think I've made this rambly point before, so sorry if it's boring.
But:
The idea that being 'rational' is the pinnacle of human achievement and immensely superior to intuitive or emotional reasoning is something Renaissance Humanists like to think they've invented. Arguably, they're just being dicks about Catholicism and the Middle Ages, but they go in for 'rationality' in a big way. It is not coincidental that they also go in for gendered education. This movement gives us the origins of the school/university system where boys and men are quite deliberately taught different subjects, with more intellectual rigour, than women, even at a very early age. Women are effectively denied the intellectual building blocks that would help them construct arguments according to principles of logic and debate. 'Rational' thus becomes a loaded word with a back-history of crowding women out.
The Victorians come along and load on another set of biases, by claiming that women are inherently irrational because our wandering wombs make us unbalanced.
I don't think this has completely gone away, and it's one of the reasons 'irrational' annoys me as a buzzword.
Plus, purely from the point of view of someone wanting good debate, if you think someone is illogical/irrational, you ought to be able to point to the flaw in their logic, and it ought to be more than disagreement.