Hoo boy, are the 30something dudes in my facebook feed pissypants about this.
So far I have heard:
well I guess I can just go to a girl’s school now because if girls can be boy scouts whine whine whine gender isn’t really a construct (and yes I corrected that)
“separate but equal” - if they have girls in there too then they have to cater to interests of both genders and that makes it a worse experience for everyone, that’s why it’s better to keep it separate (yet I can’t get them to tell me what boy-specific scout events girls wouldn’t also enjoy)
conspiracy theory - “massive pressure” from other organizations to make them admit girls (some dudes think the Girl Scouts forced the Boy Scouts to do this, apparently)
if they want to be co-ed, just join Venture Scouts (to which I pointed out that VS starts with high school, so what does that do for kids - no reponse)
Ultimately, they want to keep their boys only club they think their club will be less special if girls are there. So you know, sexism and misogyny.