^Never? He should never cut her some slack? I mean, I can understand the objections when she was assigned by admiralty to that mission. Everyone including Picard & RO objected, Which is why she had an attitude. She was being forced to participate in shady dealings, but at the end, Picard takes her in, makes her a part of the crew. Gives her a chance, based on how she behaved in coming forward during that mission. She behaved honorably, when the chips were down, & she was under the thumb of corruption. Picard saw honor in her, & believed that she could grow up enough to put behind her the impetuous person she'd been, who got her away team killed (Picard having some experience in being young & impetuous) Should Riker just ride her the rest of their service together, when in fact, she has no real trouble adjusting to Picard's command nor any of the others in command?
If we are to believe that Riker respects Picard, & his choices, & takes the lead from him, then he should have stowed the baggage & followed suit, but he didn't, & he likely never would have, had the "Conundrum" event never occurred, when they got to see through the posturing on both sides, him hating her roguish nature, & her hating his obligatory rank pulling. It's only after they drop ranks in that episode, that the 2 of them realize that the gears they were grinding against one another weren't really personal. They were chips on their shoulders that once dropped, left them very agreeable to one another
& by the by, Riker's dishonor in the Pegasus incident isn't that he was ignorantly following his captain during the mutiny. It's that later, he figured out what really went down. LONG before the events of the episode, & colluded to keep it secret by not coming forward. He let those people's deaths be for nothing, once he knew why they had died, trying to deactivate a tech that was in violation of treaty
Ro, hot head that she is, made one stupid decision that had tragic consequences, & never even defended herself. She took her lumps. Riker, was just a blind cadet, who got wrapped up in a big ugly, & when it went south, he was a party to conspiracy for the rest of his days, or at least would've been had they never found the ship. Riker came forward when the chips were down too, but his chips took a lot longer to fall than Ro's in "Ensign Ro", & that's the dishonor he must bear. That he betrayed all his dead crewmates for so long by not letting the truth come out.
Could he have come forward, realistically, & had any impact beyond getting himself removed from service? Maybe not, but it's still dishonor. He was a party to conspiracy to hide the truth from the official record & authorities, to protect the illegal secret that he eventually had to have recognized, & yet Ro comes forward almost immediately to out the corruption in her 1st mission with them. You'd think Riker might see the value in that the way Picard did, but no, not until he had it embarrassingly dumped in his lap when they lost their memories & got romantic with each other