Legislation pending before Congress would dramatically expand the federal hate-crimes law, and a number of critics are concerned that the bill goes too far. Perhaps the real problem is that it doesn’t go far enough.

Under current law, crimes motivated by bias against a victim’s race, color, religion, or national origin can be prosecuted by the federal government, so long as the victim had been engaged in a “federally-protected activity” - attending a public school, for example, or being in a place of public accommodation or entertainment. The proposed Matthew Shepard Hate Crimes Prevention Act, which passed the House last month and is pending in the Senate, would significantly broaden the federal government’s reach.

The bill, named for a gay college student beaten to death in Wyoming in 1998, would add four new categories of hate crimes to the federal code: those committed because of someone’s sex, sexual orientation, gender (or transgender) identity, and disability. It would eliminate the prerequisite of a “federally-protected activity” and require instead only the loosest connection to interstate commerce. And the proposed legislation would make it far easier for defendants acquitted in state court to be retried at the federal level - a circumvention of the Fifth Amendment’s protection against double jeopardy that has prompted four members of the US Civil Rights Commission to publicly oppose the bill.

If enacted, the law will almost certainly be challenged in court. The Constitution does not grant the federal government any general police power - prosecuting crime is primarily a state and local responsibility - and it is far from clear that the Supreme Court would go along with a congressional attempt to federalize such a broad swath of criminal law.

Which is just as well, since the new law will not serve any legitimate criminal-justice end. Every crime that would be covered by the bill is already a felony under state law. Each one can already be prosecuted and punished. Its name notwithstanding, the Matthew Shepard Hate Crimes Prevention Act will not prevent any hate crimes. Nor is there anything it could have added to the prosecution of Shepard’s killers, both of whom were convicted of murder and sentenced to two consecutive life sentences.

Supporters of hate-crime legislation often invoke the victims of such high-profile murders. After James Byrd Jr., a black man, was savagely dragged to his death in Jasper, Texas, by three white men, Senator Ted Kennedy introduced a federal hate-crime bill and brought Byrd’s daughter to Washington to testify in its behalf. But Texas authorities needed no federal help to bring Byrd’s murderers to justice. Two were executed and the third is behind bars for life.

Last month, the National Center for Lesbian Rights declared that the murder of Angie Zapata - a transgender person bludgeoned to death in Colorado last summer - showed why an expanded federal hate-crime statute was “long overdue.” Yet even without such a statute, Zapata’s killer was convicted of first-degree murder and sentenced to life without parole.

Hate-crime laws serve a symbolic function, not a practical one: They proclaim that crimes fueled by certain types of bias are especially repugnant. But that is the same as proclaiming that crimes fueled by other types of bias, or by motives having nothing to do with bias, are not quite as awful. Is that a message any decent society should wish to promote?

Suppose Matthew Shepard’s murderers had killed him for his wallet, or to prove their toughness to a gang, or out of sheer sadistic bloodlust. Would his death have been any less horrific? Would his family have shed fewer tears? Is it somehow better when a thrill-seeker burns a church than when a bigot does so? If James Byrd had been lynched by three black men, would his slaughter not have been as monstrous?

The best hate-crimes bill Congress can pass is none at all. But if we are going to have such laws, why limit them to only four, or eight, categories of victims? Let Congress expand the pending legislation to include every crime of violence - regardless of the attacker’s motive, or of the group the victim belonged to. Murders, rapes, aggravated assaults, let us learn to see them all as crimes of “hate” - not the criminal’s hate for his victim, but society’s hate for the crime.