It's a backlash against people describing atheism as a religion.lixluke said:Why go fanatic about the whole "lack of belief" ideology?
The position of most atheists is less like "I don't know if Pete's shirt is blue", more like "I don't know if there is a pot of gold in my backyart", and possibly even more like "I believe that there is no pot of gold in my cupboard."
The belief in practice of an atheist, based on absence of evidence that should be evident is not like the belief in practice of most (not all) theists, based on parental and peer indoctrination and/or purely subjective evidence. But it is a common argument of theists that the atheist belief is like the theist belief. When the atheist in return declares a "lack of belief", they are denying a lack of belief of the theistic kind.
There are exceptions of course. Some atheists do in fact hold a fanatical dogmatic belief that God doesn't exist. Unfortunately, this type are overrepresented in public discussions, and they will often deny their belief purely as an argumentative measure. For them, it's not about finding the truth, it's about justifying their existing belief.