The two main reasons I am an outspoken atheist are, firstly, I like to live in and deal with reality, no BS thanks. Secondly, I like to think that I am outspoken about the poison that is religion for my kids sakes and for the generations to come, that they don't have to deal with the lies of religion like I had to. Any other reasons people have?
Being vocal and directly confronting people delusions with facts and logic is the only way to reach the goal of and atheist world; hiding in the closet sure isn't going to do it.