The freedom of speech
http://en.wikipedia.org/wiki/First_Amendment_to_the_United_States_Constitution
is the treasured first amendment to the Constitution. It states:
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
In Britain though they can bar those who try to incite hatred through speech. Fred Phelps pastor of the Westboro Baptist Church (WBC), an independent Baptist church based in Topeka, Kansas has been denied entry to Britain.
Phelps is a bigot. He hates because of his religious convictions. He is the reason America had better hope his ilk does not gain political power here in the U.S.