Justin Timberlake has a prime opportunity to save lives in the wake of his arrest, but only if he's willing to own up to the alleged DWI ... so says Mothers Against Drunk Driving. Stacey D. Stewart, CEO of MADD, tells TMZ that JT is seriously lucky his night out in Sag Harbor, NY didn't end tragically ... with himself or someone else getting hurt. But, that being said, she's imploring the singer to use his celebrity to condemn impaired driving.