Is there anyone the president wouldn't shake hands with?

The Obama administration was quick to rebuff criticism for the president sharing a handshake with Cuban dictator Raul Castro at Nelson Mandela's memorial this week. "I think it was just an exchange of greetings as he was making his way through the podium up to speak," White House spokesman Ben Rhodes explained Wednesday, downplaying the gesture's significance.

This prompted ABC News' Jon Karl to ask an important question:

“Is there anybody the President would not…is there any world leader the President would not shake hands with?  I mean, if Assad had been on that stage, if Kim Jong-Un had been on that stage?" Karl asked.  "I mean I’m trying to gauge the principal.  He shook hands with everybody on the stage. I mean, is there any… anybody he wouldn’t?”

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