This whole thing about "was Riker right or wrong" is kind of ridiculous. It's very simple: Riker was the XO and Jellico was the Captain. Riker's job is to execute the Captain's orders, support in public, raise concerns in private. He did none of that. He almost literally executed none of his job as far as his relation with Jellico was concerned. He was insubordinate in the middle of a looming crisis.
Jellico could be a bigger asshole than anyone in history, but it's his ship and his mission, rightfully assigned in the authority of Starfleet Command and, by extension, the Federation Council. He's not required to be nice, understanding, empathetic, people-friendly, patient, etc. Riker, on the other hand, is required to carry out reasonable orders of a superior officer. Note: A change to the shift structure is a massively reasonable order for a commanding officer to make. Flying into a pulsar is not.
All this is one of the reasons that Riker is my favorite TNG character. He's the most realistic human being character in almost the entire franchise. Yes, he is talented, capable, funny, loyal,...but he's also a very flawed, stagnant, horny, ego-driven, shouty, occasionally insubordinate asshole.
So, while admittedly Riker is my favorite TNG character, he's absolutely in the wrong with regard to how he handles Jellico.
It's not even really a debate. Jellico was fundamentally doing his job and had every right and authority to execute it as he saw fit. Riker was the exact opposite. I'm not in the military or an organization tasked with safeguarding the safety and way of life of an entire civilization. That's said, if I related to my boss the way Riker relates to Jellico, I'd be fired , and rightfully so.