The Daily Kos had a good item on the Right Wing's freakout over Obama's shaking Castro's hand.
They assembled a photo gallery of past Republican leaders who warmly shook hands with supposed "enemies", including Eisenhower with Franco, Eisenhower with Khruschev, Kissinger and Pinochet, Bush with Noriega, Richard Nixon with Mao Zedong, Nixon with Brezhnev, Reagan with Gorbachev, Rumsfeld and Saddam Hussein, and many more.
But those were OK, because, well, Amurrica! Or something.
Click through for full-size version: http://www.dailykos.com/story/2013/12/10/1261625/-President-Obama-shakes-hands-with-President-Castro-at-Mandela-service-Right-wing-has-memory-lapse