You have a First Amendment right to say whatever you think. You do not have a First Amendment right to have an audience for your idiocy. It was true for the Dixie Chicks, it was true for Don Imus, and it's still true for Doctor Laura.
More to the point, you do not have a First Amendment right to prevent other people from criticizing what you said. Freedom of Speech cuts both ways.
...With a tip o' the hat to Personal Failure.