The question is whether or not PyLadies allows men to join as full members. I honestly have no clue. I'm sure it would be easy to see it that way since it is described as a group of women.
Now the question of whether all discrimination is bad is much more fun to ask.
What exactly are you looking for? PyLadies is not a dues-paying organization. There's no screening process or special clubhouse. Local PyLadies groups organize events (like hackathons, workshops, or happy hours) and people show up. Nobody stands at the door and checks your secret decoder ring to see if you're allowed in or not.
This line from pyladies.org has already been mentioned above:
> Anyone with an interest in Python is encouraged to participate!
Nevertheless, it's still a fact that if you let people know "hey, there's going to be a hacknight this week, and most if not all of the attendees will be women" -- then many women would admit to feeling more comfortable in that sort of environment, and might subsequently be more likely to show up than they would otherwise.
Even admitted that I don't how they work. Reading their page and seeing them in action are two very different things. I have not had any direct interaction and therefor made no judgement of them. If they are in fact that open then they are not discriminating.
Now suppose we are in London, and there are women who want to learn Python but due to religion or upbringing would not be comfortable in mixed company.
Neither of these cases is "discrimination" against anyone. It's not any kind of aggression at all.
It's also not discrimination when there are women who feel intimidated by the main groups and want a group that is more explicitly friendly to women.
The real question is whether those forms of discrimination are acceptable. I would argue yes for both of those cases. I believe people should be able to choose their environments so that they are comfortable in them.
I take it you also oppose cancer groups then.
You can take whatever you want from it. Not sure if you are taking from anything I said though....
Now, if PyLadies was 'no men only,' it would absolutely be discriminatory: they're making a decision based on some kind of attribute. (It would also not be perpetuating 'sexism' since discrimination against men is not societaly re-enforced.)
The real question is 'is this bad?' I don't think that many people have a particular problem with discrimination when it's _for_ women or other minorities, especially when it's not at the _expense_ of everyone who's not within that group. A "women's only" programming group doesn't harm men in any way, yet helps women. I feel like this is the camp you may fall into. It is certainly the one I do.