I'd agree, except there have been cases like this:

> The judge, Paul A. Engelmayer of Federal District Court, ruled that the rejected ad was “not only protected speech — it is core political speech,” [...] As such, the judge held, the ad “is afforded the highest level of protection under the First Amendment.”

http://www.nytimes.com/2012/07/21/nyregion/mta-violated-righ...

Here's one of the ads: http://i.imgur.com/iY0bx.jpg