They've hated each other for years now.
At one time, when the UFC was under previous ownership, Dana worked as Ortiz's manager...they were great friends....but, when the opportunity came along for Dana and his partners to buy the UFC, Dana had to drop his clients, Tito and Chuck Liddell.
Tito says Dana turned his back on him...but Dana had the chance to become president of UFC...he couldn't continue to manage fighters and serve as president at the same time.
Tito got pissy, hired some hollywood agent, started demanding a new contract, and began badmouthing Dana at UFC pay per views...Ortiz ended up out of the UFC for a while, but the two eventually came to an agreement on a new contract...but, in the contract, Ortiz made Dana agree to box him for 3 rounds so that they could finally settle their differences and move on as friends.