No, I don't think he did anything wrong. I think that the people who do are projecting what they think about sports as a pastime or as a transcendent activity full of teambuilding and Hoosier-ship and Being Like Mike and all that onto what is, at the end of the day, a job.
I don't understand this point of view.
I understand not thinking that it's a big deal. I understand the confusion of the system changing under Stevens from what it was under Doc.
But I don't understand "he did nothing wrong". He didn't show up for work, and he didn't have permission to do so. According to Stevens, they discussed the matter ahead of time, which suggests that Rondo was asked to be at the game, and skipped it. Even if that's not the case, he was AWOL, and Stevens didn't like it.
How is that "nothing wrong"? When you're a professional, you ask permission to take a leave day beforehand.
It's not a huge deal, and it certainly doesn't deserve the media coverage and character assassination that it's brought with it. However, I think it's clear that Rondo, at the very least, broke a team rule, and showed a lack of (leadership / professionalism / maturity) in the process.