White-knighting is a term often thrown around nowadays which usually means defending a person just because she is a female. I'd say that for me, white knighting means automatically jumping to defend a female regardless of her behaviour.
Never in the history of Western civilisation were women automatically given respect just because they were women. "Decent" women were respected, decent meaning chaste. Before sexual revolution, a woman was automatically presumed chaste until proven otherwise, but on the other hand, everybody knew the difference between a girl you brought home to Mother and all the others. Nowadays women are presumed to be sexually emancipated and "equal" to men.
"Decent" women in the times past signaled their chastity by the way they dressed and behaved. They were supposed to be modest, ladylike and demure, and to adhere to certain standards, for instance, a lady (meaning a chaste woman) wouldn't be seen drunk in public. She wouldn't use certain type of language etc etc. Nowadays lots of women want to signal otherwise, and are proud to demonstrate how immodest and "risky" they can be (this site shows a nice contrast between then and now, and though I don't endorse them, it's difficult to disagree with the point they are trying to make).
White-knighting for undeserving females is not traditional in any way or form. In traditional Western society these types of women would have been shamed, ridiculed and shunned and not so long ago. The idea that a traditional man should always take up the side of a woman regardless of the way she behaves is not only ridiculous, it's downright insulting to those women who still try to be ladies because it explicitly tells them that men really don't care how debauched you are.
Then there is this pernicious idea that a man should never strike a woman. A man should never abuse a woman, or another man, it's true. However, if a man is attacked and fights back, I don't see a problem with it. Women should not go around starting fights and attacking random men and then trying to pull a "I'm a delicate fragile lady" card. A lady doesn't get drunk and start bar brawls with bouncers, she stays home and does cross-stitching or plays the piano or reads a classic novel or something along the lines.
Women can't both have their cake and eat it, too, and trashy slatterns give ladies a bad name. And for those among us who still believe in "grrrl power", this might be helpful.