HERE is their contact page.
In the San Francisco Bay Area, Clear Channel owns KNEW-am, conservative talk radio home of Michael Savage, and KABL-fm, 40's, 50's music.
Wonder if Clear Channel will ever find this offensive? Here's a link to their "Know the Facts" FAQ.
Outdoor: Know the Facts
MYTH: Clear Channel Outdoor rejected ad copy from Project Billboard because it didn't agree with its political message.
FACT: Politics plays absolutely no role in reviewing ad copy. In fact, Clear Channel Outdoor actively work with groups across the political spectrum to help them reach their target audiences. That said, we reserve the right to reject any copy that would be offensive to a local community.