Board Thread:Naruto Discussions/@comment-30455007-20180203011536/@comment-734582-20180212175719

Judara wrote: This isnt about hatred Itachi plainly states that "Madara" was unfit to lead the Uchiha clan, while Obito outright states that Itachi was lying to protect Sasuke, while also clearly working against Madara's plans.

It's fairly clear that Itachi and Obito didn't like each other, and that Obito didn't like Madara.