Going back to R3x's original post, it is about protecting the rights of everyone, even those who are despised. I recall the ACLU's decline in popularity began with the Skokie, IL case. The ACLU defended the rights of the American Nazi Party to March through the predominantly Jewish community. It alienated a large portion of their supporters and no doubt hurt their fund raising. They did it anyway because of the belief that all speech, even hate speech, should be protected.
They have worked hard at the seperation of church and state. To those of you that practice a Judeo Christian religion, having the 10 Commandments displayed on a court room wall seems like no big deal. But to those who practice another faith it is. We get your version of God thrown in our faces constantly. We don't need to get it in public buildings as well.
As for the child molesters and terrorists, they deserve due process as much as anyone else.
Lapsed ACLU member.