Put it this way, there are many different types of gangs. You can choose to partake in a gang of your choosing (or theirs?) but you can also choose to not partake in a gang. Now, choosing to not partake in gangs is not a gang in its own. There is no "non-gang gang."
You have your various religions. Choosing to partake in a religion would make you religious. There is no "non-religious-religion."