You may have missed that there are other sorts of geeks in the world other than FOSS geeks. There are plenty of examples of FOSS sexism documented on the geekfeminism wiki, but it is by no means limited to FOSS.
Regardless, the existence of non-FOSS examples of sexism has no bearing whatsoever on the existence of sexism in FOSS.
Regardless, the existence of non-FOSS examples of sexism has no bearing whatsoever on the existence of sexism in FOSS.