Many do, and the most interesting conversations usually occur when that happens.I think I disagree with you.
In my mind, any agenda driven search for truth (be it pro-theism, anti-theism, etc.) absolutely has linkage to the quality of logic underpinning a person's reasoning in regards to that agenda. If the first responsibility of your reasoning is proving your agenda correct, how could you ever reason clearly? How could you not fall prey to confirmation bias? How could you ever fairly consider evidence that contends with your agenda? How could you ever fully consider the implications of your own belief? How could you live an examined life?
I think we're talking past each other a little. Just to clarify what I mean, consider the following;
1) There are varying definitions of anti-theism, and they don't all include (or limit) to broad-brush anti-religious anger. You don't have to subscribe to these definitions, but they exist, and not just on messageboards.
2) Atheism and anti-theism are not mutually inclusive. One can be an atheist and NOT an anti-theist. One can be an anti-theist, and NOT an atheist.
So, rather than discussing bias/agendas I am more making the point that the logic used in deciding to be an atheist does not speak to the logic made in becoming an anti-theist. They are two separate decisions.
Of course, someone who is logically deficient, or reactionary against religion might employ the same faulty logic in both cases.
In a more broad sense, all people have bias on virtually everything. Working through that bias is something all need to do with all aspects of everything.
I agree with 9-10ths Penguin...skepticism is part of the answer to that.