Abe, his Brooklyn accent nicely coming to the surface, subtly indicating that maybe he's getting a little lubricated, tells her there aren't any African-American copywriters, but Peggy thinks they could have fought their way in like she did. "Believe me, nobody wanted me there." I'm not going to say either of them is entirely wrong; it's a tough debate even to frame rationally, but on top of the fact that there's an argument to be made here, she clearly feels strongly about her position as a woman in the working world, so the point is that his dismissive response of "All right, Peggy, we'll have a civil-rights march for women" is both ill-advised and uncalled for. Peggy takes this as the cue to end their impromptu date, and although Abe does a lot better with his argument by telling her he only meant that women aren't currently being shot to keep them from voting, the damage is done, as she tells him he's opinionated and he's criticizing her. He tries to claim it was just discourse, and moans, "I shouldn't have let Joyce leave." Heh. Peggy does nod to let him know she doesn't hate him or anything, but that doesn't mean she's not out the door right after.