I don't think you are obviously male left-handed. My family is littered with left handers, myself included, and not one of them/us is male so I would tend to assume that you were female. As for being ignored - welcome to the club. 
In all honesty, I do not believe that many gransnetters are anti male and any who said things like you suggest were probably only joking. There is another meet-up arranged for Birmingham and one for Market Harborough - please look at the threads and join in if you can!
To be fair, if someone starts a menopause thread it's because they have an issue with something related to it and it wouldn't be appropriate for either sex to comment flippantly and, unless things have changed while I wasn't looking, men have no real experience of the menopause. You could have posted something that your own wife/mother/sister/daughter/niece found helpful/useful if appropriate!
There is no attempt to engage with any user base, as far as I can see, the members have to engage themselves. It is an undeniable fact that most posters are female so most threads are going to have a female bias to them, but, please start some more male orientated threads if you can see nothing to your liking. You never know more males might appear. 