Pop star says she will join Twitter to promote the show, which premieres in April. By Gil Kaufman Christina Aguilera Photo: Frank Micelotta/ Getty Images Is the age of the mean judge over? With the new “American Idol” panel going pretty easy on this year’s top 13 so far, it’s starting to sound like there will be more of the same back-patting on the upcoming NBC singing competition “The Voice.” “There is no good and bad,” said Christina Aguilera , one of the show’s mentors, in her first public appearance since her arrest for public intoxication earlier this month. Aguilera sat in one of the oversize swivel chairs alongside fellow judge/coach Adam Levine on Tuesday to talk up the show, which premieres on April 26. “This isn’t about tearing people down. I want to bring these people up,” she added, according to Entertainment Weekly. ” ‘The