I can understand why Garry Kasparov hearts dissidents, since he's one of Russia's most prominent himself. And he may be able to beat anyone but a computer in chess, but his logic falls seriously short here:
But the Soviet Union used tanks to quash dissent when it could. Dictatorships use force when they can get away with it, not when a U.S. president makes a strong statement.
Okay, agreed. Nothing Barack Obama says or doesn't say about the Iranian "revolution" will affect how the country's leadership, who seem to be pretty desperate to hang on to power, employs violence. But then how does this follow?
President Dwight Eisenhower might have learned that lesson in 1956 when he said nothing and the Soviets sent tanks into Budapest anyway. Likewise, in 1968 the Soviets cracked down in Czechoslovakia even though the West said little. Regardless of what Mr. Obama says, the Iranian leaders will use all the force at their disposal to stay in power.
"That lesson" is not that silence from a U.S. president will cause a dictatorship to send in tanks to quash dissidents; it is, in fact, the opposite, as Kasparov said in the previous paragraph. There is no relationship between what the "leader of the free world" says and what the leader of an unfree country does to his own people. So, contrary to the thrust of this much emulated argument, Barack Obama not issuing his "support" for Iranian dissidents will not "cause" a greater crackdown in Iran. History is being twisted into erroneous causation here, and it's being used for purely political purposes.
(image from flickr user arellis49 under a Creative Commons license)