The truth is much more complicated than that simple generalization.
{and at the time of the alleged passing of secrets, the Soviet Union was our ally in WWII}
http://www.answers.com/topic/ethel-and-julius-rosenberg
David Greenglass was spared execution in exchange for his testimony. He spent 10 years in prison and was released in 1960, and has lived under an assumed name since his release. Decades later, in late 2001, Greenglass admitted that he had committed perjury and falsely implicated his sister Ethel. Greenglass said he chose to turn in his sister in order to protect his wife and children.
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Controversy
From the beginning of their trial through the present, the Rosenberg case has been a controversial issue, with individual opinions falling roughly among ideological lines. In learned circles, there are a number of points of contention which still hold, even after the revelation of many hundreds of pages of previously secret evidence.
* To what extent was Ethel involved? As noted above, there seem to be reasons to believe that while Julius was likely involved in some form of espionage, his wife Ethel may have not been, or not to the extent to which she was convicted. The VENONA transcripts are ambiguous as to Ethel's involvement, and the government case against her seems to have rested only on the testimony of her brother, David Greenglass, who later apparently told reporters that he had perjured himself in order to lessen his own sentence and to help his wife avoid jail time. <4>
* Were they given a fair trial? There are many critics who have alleged that the political climate of the time, and the seemingly a priori conviction by Judge Kaufman of the pair's guilt, would have made it impossible for the Rosenbergs to have had a fair trial by an impartial jury. The Rosenberg lawyer, Emanuel Bloch, also made a number of massive legal blunders (such as not cross-examining Harry Gold, who in later trials was found to be highly unreliable) suggesting either his incompetence or inability to cope with such a high-profile trial.
* Was their sentence fair? The imposition of the death sentence upon the Rosenbergs has been the most controversial aspect of the case, as they were sentenced far more harshly than any other "atomic spies," primarily because they refused to confess to their alleged crimes. Klaus Fuchs, who spied for many more years than the Rosenbergs were alleged to and gave far more sensitive information to the Soviet Union, was only sentenced to 14 years in jail by comparison, in part because he cooperated with authorities and because the Soviet Union was an ally of the United States and the United Kingdom at the time he passed on information. This latter point—whether the alleged Rosenberg espionage in 1945 should be held to the international politics of 1950—is one of special contention, as some critics (the Rosenbergs' sons, in particular) have argued that the Rosenbergs were not trying to undermine the United States when they gave the USSR classified information, but rather trying to help the USSR fight against a greater enemy, Nazi Germany. In 1950, though, this distinction was not made by the U.S. judge or jury, who saw their espionage in the context of the Cold War, Judge Kaufman going so far as to blame the couple for the Korean War.
* Did they actually help the Russian program? Recent scholarship has suggested that Greenglass and the Rosenbergs actually knew very little about the workings of the atomic weapons aside from basic concepts that the Russians had already acquired through other espionage sources anyway (or would have likely figured out fairly quickly on their own once their atomic bomb project was put into full production), and compared to the information given by Fuchs and Theodore Hall, it is unlikely that the Rosenberg/Greenglass data would have significantly aided the Soviet project. Even the detailed information given by Fuchs and Hall seems to have only marginally sped up the Soviet project, as it was heavily distrusted by project leader Lavrenty Beria. This, of course, is a question not necessarily related to their guilt or sentencing.