"... that a good number of people who call themselves atheists, go well beyond simply not having a belief in God - they actively deny that God exists. "

but, you can't prove a negative, so why bother going about it?

Yes Joe, there are those... it is hard to define simple categories. Humans have more sub-categories than we have words for. Perhaps, pragmatically, 'atheist' needs sub-categories, just as 'believer' of 'Christian' do. A 'fundamentalist atheist'? to go along with 'fundamentalist Christian'? I personally try to follow the etymological rules in order to clarify the point I am making, but it ain't easy when everyone has their own notions of what words convey.

There really are, as Jack Blandiver notes, those who simply don't fight a battle that they see can't be 'won' by either side. I call myself a skeptic because that word still carries the connotation that I wish to express.