Why does Mr. Kumar not believe in God?

Mr. Kumar, Pi's Biology teacher, is an atheist. He thinks that life is explained scientifically rather by God or the supernatural:

"Religion?" Mr. Kumar grinned broadly. "I don't believe in religion. Religion is darkness."

Darkness? I was puzzled. I thought, Darkness is the last thing that religion is. Religion is light. Was he testing me? Was he saying, "Religion is darkness," the way he sometimes said in class things like "Mammals lay eggs," to see if someone would correct him?