Naperville Moms Meetup- NO DADS ALLOWED

I'm a stay at home dad who just moved to Naperville with the family. Recently had a really nice time with the kids at the playground with what turned out to be a Naperville Moms meetup group. A few of the moms invited me to join the meetup group and said they had even spoken with the organizer (thanks open minded parents!). What a shame that I received the following response to my request to join: 
"Unfortunately, our group is very large right now and due to size constraints we are not opening membership up to stay at home dads or other caretakers at this time."
But I guess moms are still welcome. 
Really a shame that this particular playground gender bias still exists.