A couple having sex on their first date is a dichotomy since the man is usually commended for it, yet the woman is labeled a slut more often than not.
By Fannie
Dichotomy
1. Division into two usually contradictory parts or opinions.
2. Astronomy. The phase of the moon, Mercury, or Venus when half of the disk is illuminated.
3. Botany. Branching characterized by successive forking into two approximately equal divisions.