But do you spend a great deal of time arguing about his existence? There seems to be a difference here.
No one over the age of five believes in Santa Claus. However, at least 98 percent of the population believes in some kind of deity (athiests make up something less than 2 percent of the population). Arguing against the existence of God does not indicate a hatred of the Almighty (which would be wierd -- you can't hate something you don't believe in). It could instead be seen as a reaction to the in-your-face proselytizing practiced by some of the more aggressive evangelical types. Hell, being Catholic I've often found myself mocking the "are-you-saved" crowd, especially when they're attempting to "save my soul."