If Robert Price can consider himself an atheist Christian then why not have secular Islam too?
Some Jews and Muslims are atheist/agnostic yet retain their ethnic labels in which they may commit to a devotion of practice and ritual based on ethnic heritage yet do not believe in the supernaturalism of deities. It seems to me the emphasis is based more on the history of the heritage rather than pious deification. Makes sense I guess.
I tend to think of it as soft or watered down ancestor worship.