It's "incline", the subtext is: "Reader, you might start thinking of a certain common stereotype at this point, but don't do that, because my argument is very different, and that stereotype is irrelevant or possibly untrue."

Compare to: "A pick-up truck is a useful thing to have, not because you are insecure about your genitalia, but because you can take home bigger products from IKEA."

No, "tend" means "incline" here, but the normal grammatical reading of the sentence does not suggest wives have profligate tendencies.