You can opt out of all announcements from a Meetup Group. We used to require that you receive announcements from organizers, but we recently allowed you to unsubscribe from those as well as the automated announcements.
Meetup does review every new group and we discourage using the service for one off events. That said its not our policy to reject them out of hand and there should have been contact from a person on our community team prior to the decision to remove the group. In this case 'remove' most certainly doesn't mean delete. There's plenty of developers at Meetup that understand the value of not deleting data. The Meetup Group has been flipped back to approved and is accesible on site.
We are sorry when this happens, still, review of new groups is important to us -- there's a lot of new Meetups proposed every day that we really don't want to host on our platform. We have technology in place to help us with automatic classification, but while improving, its imperfect and in this case our safeguard of manual review was too quick to reject the group.