All of this comes against the backdrop of a troubling Congressional antiterrorism bill that also focuses on the Internet. The Violent Radicalization and Homegrown Terrorism Prevention Act, which passed the House last year by a 404-to-6 vote, would establish a commission to study the terrorist threat and propose legislation. The bill, which the Senate has not acted on, has a finding that the Internet promotes radicalization and terrorism.

Although the report by the homeland security committee stopped short of making recommendations for reining in online speech, it did ask “what, if any, new laws” were needed. The answer is that no new laws are needed  or justifiable  any more than it would be tolerable to enact laws restricting speech over the telephone, in a newspaper or a book, on a street corner, or in a church, mosque or synagogue.

While it is fortunate that Mr. Lieberman does not have the power to tell YouTube that it must remove videos, it is profoundly disturbing that an influential senator would even consider telling a media company to shut down constitutionally protected speech. The American Civil Liberties Union has warned that the “Homegrown Terrorism” bill and related efforts “could be a precursor to proposals to censor and regulate speech on the Internet.”

Not only do these efforts contradict fundamental American values, it is not clear if they would help fight terrorism. Even if YouTube pulled down every video Mr. Lieberman did not like, radical groups could post the same videos on their own Web sites. Trying to restrain the Internet is a game of “whack-a-mole” that cannot be won, says John Morris of the Center for Democracy and Technology. Having the videos on YouTube may even be a good thing, because it makes it easier for law enforcement officials, the media and the public to monitor the groups and their messages.

Terrorism is a real concern. All Americans know that. They also know that if we give up our fundamental rights, the terrorists win. If people use speech to engage in criminal acts, they should be prosecuted. Cutting off free speech is never the right answer.