The memorial service of Nelson Mandela has, unsurprisingly, led to one of those amazingly dumb pseudo-controversies that have become so tiresomely predictable. It was sparked by Obama's decision to shake Raul Castro's hand when the two leaders found themselves in the same place at the service. According to Mona Charen at National Review, the handshake "makes the stomach turn." Meanwhile a Fox News host has just strongly implied that the handshake is an insult to Mandela's beliefs about freedom. Although this brouhaha is no doubt politically motivated, the issue of presidential handshaking does come up annoyingly often.
Unlike in the case of, say, sanctions, handshakes are purely symbolic. Does shaking hands with bad people send the "wrong message?" What "does it say" for the president to shake the hand of X? The American embargo and general isolation of Cuba is a stupid policy that has done no favors for either the Cuban or the American people. That being said, there is a reasonable argument as to why the United States should have a double standard about Cuba and Russia, or Cuba and China. The argument essentially states that we can't isolate everyone who should be isolated, and therefore we should only isolate those whose isolation will not cause major diplomatic and economic damage to the United States. As I say, it's at least an argument.
However, the idea that the president should not shake hands with Raul Castro, or Arafat, or any current or former antagonist of the United States, is silly beyond belief.
In the case of sanctions, you are dealing with practical policy issues. In the second case, you are not. However, when you are dealing with a symbolic matter, consistency matters. And since no one seems to be arguing that the president should shun the leader of China or Russia or Saudi Arabia or the vast majority of the rulers from countries just as bad as Cuba, well, the argument makes no sense. Obama already "sends the message" that the president will shake hands with bad people. Shaking Castro's hand is irrelevant.
The only remaining argument is a variation on the sanctions argument: you can't avoid shaking hands with everyone so you might as well avoid shaking hands with some people. Again, this would have more weight to it if shaking hands had any importance beyond the symbolic. Perhaps Mona Charen's stomach reacts every time Obama shakes hands with a bad guy, but somehow I doubt it. No American president, including Obama, will consistenly shun unsavory world leaders. Who cares if he shakes Castro's hand?