Comment by theorique

Back in school, my sports coaches would sometimes refer to all male groups as "ladies". However, I suspect this is not what you're talking about ;)

As much as anything, I've heard many women refer to mixed gender groups as "guys" or "dudes". A lot of this "definition creep" is actually due to women themselves. Probably this is because the male identity is viewed as a source of power, and women seek this out and aim to identify with it.

In other words, I don't think the use of "guys" generically is being driven by sexist men. I think it's being driven by blurring of gender roles and definitions, and adoption of these generic terms by women.