Clear Channel owns most of the Billboards in my part of the country (AZ). They have all kids of ads, but they also have 'pubic service' billboards like "ONE NATION UNDER GOD" and "OUR LEADER".
Maybe they would allow some liberal slogan billboards.
At least they could allow some religious left slogans/Bible verses, such as the ones cited by Katherine Yurica in her article "The Blood Guilty Churches" which is a detailed criticism of the Bush policies using only the Bible.
Blood Guilty Churches
Why Bush’s Agenda Is Immoral and an Abomination to GodBy Katherine Yurica
http://www.yuricareport.com/Religion/TheBloodGuiltyChurches.htmlexcerpt:
"George W. Bush, his administration, the Republican controlled congress as well as the Republican Party itself, and most of the churches in America (including evangelical, Southern Baptist, Pentecostal and Roman Catholic),
stand indicted—not by men—not by this writer—but by the very Holy Scriptures the religious-right and Mr. Bush profess to uphold."
"Weighed against the Bible, the Bush actions are not only morally corrupt—they are unchristian and unbiblical to the core. In this essay, the Bush agenda is weighed on the scale of God’s standards and it is found wanting."
http://www.yuricareport.com/Religion/TheBloodGuiltyChurches.html