There’s something that really grates on people when admitted thieves, racketeers, and murderers are given lenient treatment, and sometimes cut lose entirely, for cooperating with prosecutors. If you do the crime you should do the time. Right?

So there were no widespread protests back on August 11, when U.S. District Court Judge Robert J. Sullivan refused a request by federal prosecutors in Manhattan to free Bernard Madoff’s right-hand man, his CFO Frank DiPascali Jr., on a $2.5 million bond. “I’m glad,” one Madoff victim told the New York Daily News as DiPascali was tossed back in the clink.

Sullivan said that DiPascali was a “flight risk,” but I think we all know what was going on here. Sullivan was engaged in a bit of low-risk showboating, trying to demonstrate in a headline case that he was tough on white-collar crooks.

Popular as it was to deny bail, it was an immense mistake. Whether Judge Sullivan or Madoff’s victims like it or not, prosecutions of the Madoffs of this world and their accomplices hinge on the ability of law enforcement agents and prosecutors to enlist cooperating witnesses—“rats,” in cop parlance. Yes, cutting deals with admitted crooks is galling, but that is often the only way to prosecute the people involved in a criminal conspiracy, particularly a complex one like this.

Fortunately, Judge Sullivan has a chance to reverse his error today, October 27, when a hearing convenes at 4 p.m. to reconsider the prosecution’s bid to have DiPascali released on bail. This time he had better think of the consequences of his action for the way the society deals with the worst white-collar crooks.

That’s how criminal conspiracies have been prosecuted throughout history. Back in the 1930s, for instance, the prolific Brooklyn murder mob, Murder Incorporated, was taken down when prosecutors cut a deal with one of the leaders of the mob, a nauseating character named Abe Reles. He was one of the worst murderers in New York history, but that didn’t prevent prosecutors from turning Reles into their star witness. More recently, cooperators have been crucial in nailing criminal conspiracies as diverse as the Charles Manson “family” to New York’s five Mafia families to Enron. That’s the way the system works, and it hinges on the ability of prosecutors to make deals with some pretty awful people. DiPascali is no choir boy, but he’s no worse than any of the cooperators that pollute the pages of criminal justice history.