The reason churches are not taxed is separation of church and state. The state is supposed to say out of religion and the church is supposed to stay out of politics. I deem it fair then when the church sticks its nose into politics that church loses its protection from taxes.
In fact there are grounds for just this, the 1954 federal Johnson Amendment prohibits a pastor from talking about candidates from the pulpit in light of Scripture.
In fact there are grounds for just this. The 1954 Johnson amendment limits the ability of churches to speak of or endorse candidates or face taxation.http://en.wikipedia.org/wiki/Johnson_Amendment
I hope the IRS has their ears perked towards this guy.