I may be way off the mark here as it is only a thought that has popped into my head just now.
As an atheist, I have quite strong feelings about religion and find it all quite bizarre and absurd. However, if I said that to someone religious in my office I could potentially be sacked due to criticism of their protected characteristic.
I just don't feel it is the same as saying a similar comment about disability, ethnicity, sex etc. Of course I don't think anyone should be actively discriminated against because of their religion, but no more so than because of the colour of someone's eyes. It doesn't effect anyone else. It's more the fact that I as an atheist cannot voice my opinion about religion without insulting a protected characteristic and vice versa.... Yet its generally OK to believe that God doesn't exist. Odd!
Thoughts? Have I missed something? Am I being far too black and white here?