Hello, friend, and welcome to Less Wrong.

I do think you should start a discussion post, as this seems clearly important to you.

My advice to you at the moment is to brush up on Less Wrong's own atheism sequence. If you find that insufficient, then I suggest reading some of Paul Almond's (and I quote):

great atheology

If you find that insufficient, then it is time for the big guy, Richard Dawkins:

• The Blind Watchmaker
• The God Delusion

If you are somehow still unsatisfied after all this, lukeprog's new website should direct you to some other resources, of which the internet has plenty, I assure you.

Edit: It seems I interpreted "defend myself" differently from all the other responders. I was thinking you would just say nothing and inwardly remember the well-reasoned arguments for atheism, but that's what I would do, not what a normal person would do. I hope this comment wasn't useless anyway.