[Anechoic]

Would you consider it sexist if someone started a developer list only for people that identify as male?

It really depends on the context. If the list was started just to encourage juvenile behavior, than yes. If it was started to address real issues that were specific to male developers (perhaps paternity leave/care issues), than no.

There are mens groups in a number of occupations where men are underrepresented (primary school and nursing being the most prominent).