Have you read Inhuman? That's not what's happening at all. The doors of Attilan are open to any Nuhuman who wants to join, other than that Medusa has no strict policy of rounding them up. It's their choice, which is kind of a big deal in the book. And Black Bolt isn't even King right now, so he's not even involved with "recruiting". The only one doing recruiting is Lash, who is a bad guy.