Not sure why the above didnt post as a hyperlink, but it is from a liberal site that popped up when I did a search of this subject.. Proponents of free speech oppose the law as well.
Some of their contentions include:
“The measure was opposed by the U.S. Commission on Civil Rights on double-jeopardy grounds...the bill’s sponsors seek to use it to reprosecute people in federal court who have already been found innocent of hate crimes in state court, taking advantage of the “dual sovereignty” loophole in constitutional protections against double jeopardy.
Civil libertarians ...also object to the bill on double-jeopardy grounds.
Such re-prosecutions can be an enormous waste of money, and grossly unfair to the people who are reprosecuted, driving them into bankruptcy to pay lawyers to represent them all over again when they have already been found innocent in state court after an expensive trial.
When the government re-prosecutes someone, it gains an enormous tactical advantage over the defendant from using the prior prosecution as a test-run, even if the defendant is innocent — making a guilty verdict possible even if the defendant is in fact innocent.
The bill contains speech-related provisions designed to allow prosecution of people who are not violent and do not intend to cause hate crimes, but whose speech inadvertently incites a hate crime by some other...
For now, courts are likely to block such prosecutions on First Amendment grounds, under the Supreme Court’s Brandenburg decision banning prosecutions of people whose speech unintentionally incites violence or other illegal acts (and the federal appeals court ruling in White v. Lee faithfully applying that principle to speech that incites violations of federal civil-rights and anti-discrimination statutes).
But if the ideological composition of the Supreme Court changes substantially, it is conceivable (although far from certain) that that could change. Although the provisions will probably prove unsuccessful in censoring speech, it speaks volumes about the mindset of the hate-crimes bill’s backers that they would even try.
The bill also raises serious constitutional federalism issues under the Supreme Court’s Morrison decision...”