Why Atheism instead of agnosticism of some sort

[Tiberius]

This goes agianst the second law of dynaimics. At one point in time the universe had complete order, now it is slowly going to disorder.

I'll assume you meant "second law of thermodynamics", but you are still wrong. It only goes against the law if it is assumed that the law has always been around. If the law came into existence at the point of the Big Bang, then whatever happened "before" (if there was a before) wasn't under its influence.

I watched a documentary recently on how a lot of physicists are now rejecting the idea that the Big Bang was the "start" of everything, and moving more towards whether there were events before the Big Bang. It went into the realm of multiverse theory, so it can all be taken with a pinch of salt, but it's very interesting nonetheless.