Under our First Amendment, a censorship law would have to be written in broad general language and could not be directed at specific religious, ethnic, racial, or political groups. Any such law could be misused by politicians to censor their political enemies or other "undesirable" groups.
Dershowitz, Alan (2008). Finding, Framing, and Hanging Jefferson: A Lost Letter, a Remarkable Discovery, and Freedom of Speech in an Age of Terrorism. John Wiley & Sons. p. 191. ISBN0470450436.