@Merry Andrew,
Merry, I think you are completely missing my point. It is the gender stereotype implicit in the term "gentleman"-- where men are judged by a different standard because they are men-- that I am objecting to.
Can you understand why some people consider the term "ladylike" sexist?
Isn't trying to instill "ladylike" behavior in our female offspring... where being a "lady" means girls are limited in their behavior (in ways that boys aren't limited) part of the problem. I feel the same way about each of these terms.
The terms "lady" and "gentleman" are part of society's mechanism to force gender-based views of "appropriate" behavior on us. I don't accept this for myself and I don't force this on my kids.