White House deputy press secretary Josh Earnest warned critics of President Obama that they should not make Hitler comparisons when discussing modern political events such the president's handshake with Raul Castro prior to his remarks at Nelson Mandela's memorial service.

ABC News White House Correspondent Jon Karl questioned Earnest about Republican Arizona Sen. John McCain's remarks comparing Obama's handshake to that of former British Prime Minister Neville Chamberlain's handshake with Adolf Hitler just before World War II.

"I think even in the few number of times that I've stood at this podium, I've been asked about people who have tried to draw connections between recent political events and the terrible reign of Adolf Hitler," Earnest said. "That is a dangerous and usually unwise thing to do in public."