The part of this interchange that always strikes me most is FW's sister's response, "But I hate to hear you talking so like a fine gentleman, and as if women were all fine ladies, instead of rational creatures. We none of us expect to be in smooth water all our days." Mrs. Croft's arguments seem more interesting to me than FW's.

Of course FW is the hero of the story, and if JA just wanted to give Mrs. Croft an opportunity to speak up for women's rationality, she could have put FW's words into someone else's mouth (Charles's, maybe?). I like your idea that maybe Anne's rejection contributed to his thinking that women are irrational -- though ironically, her rejection was caused by perhaps excessive rationality.