On drug violence, Mexico must look inward/ Ruben Navarrette Jr. is a CNN.com contributor and a nationally syndicated columnist. CNN, 18 de m ayo de 2012 It used to be that when Americans thought of Mexico, they imagined a festive getaway where margaritas flowed, mariachis played, and every day was Cinco de Mayo. Not anymore. Horrifying stories of random shootings, mass beheadings and mass graves have become commonplace. Gunmen think nothing of mowing down a couple dozen teenagers in a disco with machine guns and tossing grenades indiscriminately into crowds during holiday fiestas. Mexicans have almost become immune to carnage, it seems.