“I completely agree, darling.” “And by charity, I mean: What can be done for us ?” Move over, Kim and Kanye — Ashton Kutcher and Mila Kunis may just be Hollywood’s most obnoxious couple. Case in point: their behavior at a recent Red Nose Day charity event at California’s Universal Studios. “It was a fundraiser for kids, but both he and Mila acted like kids themselves — spoiled, bratty, rotten ones,” an insider tells In Touch of the diva duo’s “ridiculous demands.” Mila, 32, set the tone early when, rather than mingle with good-hearted A-listers, the Bad Moms actress “demanded their own green room backstage because they didn’t want to share.” She also “snapped at production assistants” and at one point literally led her husband, 38, around…