@OP: anecdotal evidence is anecdotal.
The simple truth is you quoted ONE guild that has that discriminatory rule. Links to the "LOTS" of guilds with the same rule would go a long way towards the credibility of your claim, otherwise this post just sounds like a poor attempt at trolling (or a seriously misguided attempt at starting a discussion).
Take <Paragon> for instance, the TOP EU raiding guild for all of Cata (and overall top for 2/3 tiers).
Anyone would be hard pressed to not refer to them as Hardcore or Heroic (depending on which term you referred to when you used the abbreviated 'HC' in your topic title).
One of the MAIN broadcaster and top member, Xenophonics, is a female.
My guild, whilst not Hardcore, is most definitely a HEROIC raiding guild (completed all t12 & t13 heroic content whilst it was current, and most of it 'pre-nerf').
We have had around 5 female RAIDING members over the course of Cata.
As you can see, my anecdotal evidence disproves the possibility of a generalization that either Heroic OR Hardcore guilds do not recruit females. (Of course, I'm not 100% sure whether you were generalizing that or not).