How can you “trademark” or “copyright” a common phrase?
But you can trademark a phrase. Coca-Cola (I think it was them) trademarked "Ah-ha!" or something like it, because they used it on their bottles. It doesn't mean no one can say or write it. It only means no competing soft drink company can use it on their bottles.
Trademarking a political statement, or any statement, is harder to TM, because it runs afoul of the First Amendment. I don't think you can use copyright or trademark to hinder speech. Copyright has a Fair Use exception, and trademarks simply wouldn't be protected to hinder an expression.