Humor the man, fellas.
Picard is a master diplomat but he's not perfect. If Sisko is attacking him on Wolf 359 and not backing down, Picard will, after exhausting all other options, turn the other cheek and walk away. Sisko isn't being reasonable - the man was assimilated by the Borg. Worf will stay out of it. He knows Picard is in the right, but he does not want to embarrass his current superior and friend.
But Picard is not perfect, and in the interests of getting us to where the intent of the original question wants us to get, say Sisko doesn't accept Picard's walking away and decides to force a confrontation. ...He's a formidable man, he can make it happen, and say on this drunken, non-synthaholic, night after a long, mind-fucking, mission and the anniversary of his wife's death, he really lays into Picard, who himself, drunk and back from such a mission and on the anniversary of his greatest tragedy, he takes the bait.
Besides, the occasional fight is good for the soul.
But for whatever reason, Worf now needs to take a side. He can't smash their heads together for acting like such asses...say due to injuries sustained from his last mission. And say Picard and Sisko don't know they're putting a friend and subordinate in an unfair situation. And say the whole argument has been witnessed by a cadre of hard-liner Klingon generals who Worf needs to win over and won't accept a peaceful solution, nor give a shit about how at fault Picard was for his actions as Locutus. Worf simply needs to pick a side to prove to them that a Klingon can choose a course of action, even a wrong one that leads to his damnation, after working with the Federation for so long, because, to them, damnation is preferable to indecision. They're both Klingon and meatheads - that's how they roll.
So choose, Worf.
I say he sides with Picard. He owes his life to both men, but though his professional loyalty is owed to Sisko, this is both an unprofessional situation and Sisko is in the wrong for blaming Picard for his actions while assimilated. Sisko is a reasonable man; come tomorrow morning, he'll see the err of his ways. And the meatheads will continue to support Gowron or Martok in battling the Dominion.
Let's make things worse for ourselves. Say the disagreement wasn't about Wolf 359, Locutus, and Jennifer, or anything clear or logical. Or that despite there always being other options, again here Worf is going to choose one man over the other purely out of loyalty, because that's the question, right, who Worf is more loyal to - not how he would handle a sticky situation...I haven't given him enough credit...Picard may be a master diplomat and Sisko a Starfleet captain in his own right, but Worf too could figure some way of reminding the other parties what asses they're being. Everything's really only about asking who Worf's more loyal to.
Worf would choose Sisko because he's his current superior and he's erring on the side of maintaining good blood with his superior officer and architect of a war.
That too is a copout.
...He'd choose...um...uh...er...see the thing is...ah...mmmm...uh...Picard. He's friends with both men, but Picard was also a mentor during his formative years as an officer. Plus he later returned to serving with him...though I think that's stupid, and he should have remained an ambassador or continued his Horatio Hornblower rise up the ranks.
