Justin Bieber and Scott Disick fight

Scott Disick may have kept his cool during reports of ex Kourtney Kardashian dating Justin Bieber, but an insider says that behind the scenes, he's fuming! A source tells HollywoodLife that Disick, 32, is mad as all get-out at the sassy, 21-year-old pop singer for getting involved with the mother of his three children. "The only place Scott wants Justin to go to is to hell," a Disick pal tells HollywoodLife. "He doesn’t want to be bothered with Justin at all. So he tries to avoid talk of Justin or thinking about Justin." Kourtney Kardashian and Justin Bieber Kourtney Kardashian and Justin Bieber. (Photo Credit: Splash News) Kardashian, 36, reportedly had a fling with her much-younger party friend right after Disick got out of rehab for drug and alcohol abuse. The unlikely pair were seen leaving clubs and restaurants together and dancing while they were out, and Kourt was spotted walking out of his hotel late one night looking disheveled. RELATED: Scott Disick and Kourtney Kardashian Are Working on Their Relationship, Source Says Scott is now apparently dating model Lina Sandberg, but that doesn't mean he likes the idea of Kourtney being with anyone else. "It does nothing positive for him and Scott wants to live a positive and sober lifestyle right now," the insider adds.