'Can all Atheists be lumped together?'

Sure, they're called 'unbelievers', silly!

No we're not! You see, this is the whole problem with these bitter non-atheists: they simply have to define everyone on their terms! It's a sort of insecurity, I suppose. As Musket points out, belief is not the default position of the human race. Rather, it's a baleful bolt-on which does nothing save instil fear and stunt the intellect.