In the midst of the riots that have raged across Los Angeles in response to the Trump administration’s raid to apprehend criminals, Mexican flags have emerged as a prominent emblem of the rioters’ lawless defiance.While the New York Times gushed that the rioters’ usage of the flag represented “pride in their heritage,” most Americans saw it for what it was: a symbol of conquest. But many leftists are now making that very argument, that it represents a reclamation by Mexico of land supposedly “stolen” by the United States.This week, Gerardo Fernández Noroña, the president of the Mexican Senate, adopted that...