HANK: I thought you were busy teaching girls to blow up basketballs. When did this turn into a desire to ruin wrestling?
PEGGY: Oh, give me a break. I don't see how having a girl on the team would ruin it. Did a woman judge ruin the Supreme Court?
HANK: Yes, and that woman's name was Earl Warren.
That even outclasses The Simpsons' take on the late Chief Justice Warren (Marge: "Earl Warren was never a stripper!" Homer: "Now who's being naive?").
The line is, if a google search is any indication, pretty popular on the right side of the blogosphere, but the episode itself (which may have the most instantly-quotable lines of any King of the Hill episode) is actually a good one for "King of the Hill Democrats," as it's quite liberal in a non-preachy way, and the antagonist is the sexist coach who declares that Title IX was "Dick Nixon's biggest mistake":
PEGGY: Title IX of the Civil Rights Act clearly prohibits sex discrimination in public schools, and guarantees equal athletic opportunities for all boys and girls.
COACH: Yeah, well, Roe v. Wade doesn't apply to my wrestling team.
PEGGY: Oh, I think you'll find it does apply.
(Peggy and Connie leave the office.)
CONNIE: Mrs. Hill, wasn't Roe v. Wade --?
PEGGY: Yeah, I know, dear, but you have to pick your battles.
The best exchange in that episode is probably the one after Bobby tells Hank and his friends that Connie's presence might cost him a regular spot on the team:
HANK: It's all well and good to talk about equal rights until some man loses his job. How is that equal?
BOBBY: Yeah, and it's worse when they take away our favors, 'cause we're used to getting them.
BILL: Now hold on, Hank, I'm all for ladies wrestling, except when they do it in pudding. That's just demeaning to the human beings who make pudding.
DALE: Ever since they held that big women's conference in Beijing, co-ed sports has been the number-two priority on the international feminite agenda. Want to know what the number-one priority is? Co-ed bathrooms. It'll be a cold day in hell before we institute that in the Gribble home.