I think you need to look a little deeper - Warnock had his favourite in Isiah Jones at RB for Boro - didn’t play him. Conti never wanted him and refused to play him and the Leeds boss played a back 4. It’s easy to roll out the “attitude problem” excuse to justify your decisions.
Cooper played to his strengths as a wing back, all but took defensive duties away from him and was prepared to put an arm round him.
In summary his issue seems to be not playing or not given what he perceives as a fair chance and he has to play in a side that plays wing backs. I get that he should work on the defensive side of the game which may have been a problem for some managers but there is no denying Conti was A twat with him and the Leeds move was a mistake.