I'm answering while I'm looking for a resource or web site.
What I've learned is that our First Amendment prohibits the government from making any laws prohibiting our freedom to live and express our religion. The ACLU seems to have made it their mission to confront pastors and priests with threats of having their tax-free status removed. That's not how it works.
Our First Amendment rights say we can express, live, and talk of our personal beliefs even in the "public square."
Like I said, I'll revise my post when I find something that will be useful.
-- Update --
Check on: http://www.alliancealert.org/2012/10/30/should-pastors-re...
Pastors and priests (rabbis, etc) have every right to speak what their beliefs, their opinions, and what they want to teach; short of treason. God bless all of our religious leaders!
-- New update --
Our First Amendment Rights, to be exact: "The First Amendment (Amendment I) to the United States Constitution is part of the Bill of Rights. The amendment prohibits the making of any law respecting an establishment of religion, impeding the free exercise of religion, ...".
Telling pastors they do not have freedom of speech at the pulpit is like saying they do not have the "free exercise of religion".