Evidence points to the opposite rather. When he broke free of the mind control he went straight back to being racist and an @$$hole at times where he shouldn’t be one. Thus can prove that working with the Forsaken was him going “The enemy of my enemy is my friend, for now.” Had he been less racist and more sensitive in diplomatic terms, that could weigh in proof. Even realizing that the Dreadlord sullied his name and attempted to mend bridges would have been a bonus. However he was not, and was using the Forsaken for his own ends and was more than likely planning a backstab. Was he planning a backstab? We will never know and can only guess with good evidence, for Sylvanas just shot first.