I do not see any evidence of atheism being a mental illness in that article. Furthermore, there seems to be a theist virus going around whereby the religious people are ironically referring to themselves as logical and reasonable because they believe in a god whereas nonbelievers are illogical and unreasonable because they refuse to believe in a god. The silliness that comes from theists when they are confronted with being incapable of accepting the senselessness of their beliefs is absurd.
"Never trust a fox. Looks like a dog, behaves like a cat."
~ Erin Hunter
~ Erin Hunter