To be fair, he's possibly sort of obliged to go with him in order to provide appropriate support. I don't exactly know how it works in the world of policing where if one officer wants to intervene and the other doesn't, whose word counts. I would assume if equal rank, an officer has the right to intervene irrespective of his partner's wishes, and the partner just has to suck it up and provide backup. And maybe ask for a new partner in future.
I wouldn't go too harsh on the partner. He might have failed to dissuade the arsehole from a pointless intervention, but it also needs to be recognised that he had the right idea to just let it go.
Well, that's one way to look at it. The other would be when does it become this "good" cop's duty to intervene when his partner is escalating a nonissue into a full-blown situation? Assuming equal rank, he easily could have come between his partner and the victim, excused the victim and reigned in his partner, at least that could have been his course of action. Had his partner insisted on running down a capital jaywalker, it would have exposed him as irrational, over-zealous and unfit to wear the badge let alone wield a weapon.
Inaction/complacency in this case was complicity. Don't we praise children who stand up to bullies on another's behalf? Was there no duty for this officer of the law to do the same? So while clearly not as overtly at fault as his partner who instigated the altercation, I don't think it's "too harsh" to hold him to account. At no point did it cease to be his duty to protect a citizen, but he failed in his duty, and someone died for committing the same "crime" that's rarely punished because millions of people commit it every day without even realizing it.
Fun fact, some lesser misdemeanor crimes are actually REDUCED to "jaywalking" by judges so as not to mar an otherwise decent person's criminal/driving record.