He already signed the contract but he's suing Golden Glory after realizing he was getting screwed into a Fedor/M-1 type contract when he hired a lawyer to go over it before meeting with the UFC. He's also suing them for owing him more than $151,000 in back pay from not being paid for his K-1 fights last year.
Now if Bas' side of the story is true then yes it was disrespectful for Overeem to talk down to his old coaches like that. However, can anyone justify giving a camp 35% pre-tax of all earnings? No camp in the US comes even close to that and Overeem found out once he started looking at camps over here.