What do Big Pharma ads on TV and Diet Coke have in common? Both are targets of Robert F. Kennedy, Jr., the new head of the Health and Human Services department. In his early efforts to press the “Make America Healthy Again,” Kennedy has singled out two seemingly different issues: those ubiquitous television ads for pharmaceuticals, and whether people on federal food assistance programs should be able to buy soda and junk food on the taxpayer dime.