I take your point nailit, but I don't waste any time thinking why anyone would challenge me about my absence of faith - certainly in my personal life, no-one does.
I attend Mass on Sunday mornings with my wife, and I guess the friends we have there assume I am a Christian, and I have no problem with that. I would not be a hypocrite about it - if asked I would confirm that I don't believe in God, but that hasn't happened yet.
As far as debates on here, the 'serious' Christians have their views, which I respect of course, but I do dive in when they are being pompous and ignoring any attempts to debate with people.
I think the Christian faith encourages broadly similar belief systems in its followers, which tends to lead to their arguments being similar as well.
As an atheist, I enjoy the luxury of having nothing to defend, or to encourage other people to believe in, and I am delighted to live my life without the endless questioning of how a 'loving' God can allow such horrible things to happen to his 'children' on a minute by minute basis.