Many Americans were offended by Sen. Bernie Sanders’s recent praise of Fidel Castro. Perhaps gratitude is in order instead. By candidly sharing his opinion of Cuba, Mr. Sanders exposes the depth of his socialist views.

Mr. Sanders’s enthusiastic support for the Socialist Workers Party in the 1980s is well documented, as is his endorsement of Castro and Nicaraguan Sandinista Daniel Ortega, both of whom were Soviet pawns during the Cold War. On CBS’s “60 Minutes” on Feb. 23 we learned that Bernie’s ideology hasn’t changed much...