Because the point of the Ex muslim tag is to differentiate between ex muslims, and others, not to differentiate between every group itself.
Since this is an ex muslim forum (which is not to say that all aren't welcome) it's important to keep track of who they are, so that we know how many ex muslim members we have and obviously to spread the love as new ex muslims realize that there are loads of fellow ex muslims here.
There is something positive about seeing that huge list.
