Comedians are notoriously wounded creatures, often seeking approval in whatever form they can get it, and Johnny Carson was no different. Sure, he represents the ne plus ultra of a certain generation of comics, but that didn’t absolve him of the sad, strange burden of maternal indifference. American Masters Johnny Carson: King of Late Night, which airs on PBS Monday May 14, explores this and other aspects of Carson’s life and career, and you’ll get a sense of his mother’s unsmiling influence in this advanced clip. Heeeeere’s Johnny’s lingering insecurities …