Based on One Piece Chapters 843, 844, and 845.
This will be a tragedy. You have been warned. Also, Character Death. Again, warnings now.
Usopp had had enough of this. He was sick and tired of the name calling, the blame game, the fighting. He stepped in between Zoro and Sanji in the middle of their fight. He was no longer that weak coward who'd run in between them right before they fought Arlong. It might have taken all he had not to get crushed by the blows but he managed to fend them off. His arms were shaking from the effort but he pretended he was merely shaking with rage. It wasn't far off.
"No. No." He snapped, turning to glare at Zoro. "You don't get to judge. Not again. You don't know what it's like, to be pushed to your limit that you see no other way out but to quit the crew. You don't get to judge."
He wasn't done yet, however. He whirled around, rounding on Sanji, and gave him his fiercest upper cut. It was clear the skilled fighting cook wasn't expecting it. None of them were. They all still saw him as he'd been in the past; weak, a coward. Unable to defend himself and worse, during that moment when he'd needed them most, unable to support Luffy.
"And you. You don't get to act like nothing's happened. You better than most of us, understood exactly what you were doing when you tried to leave. You were here to see how Robin's betrayal, how my betrayal, effected Luffy. You were trying to do it as painlessly as possible for us? Cut the bullcrap, Sanji! If you were going to leave, at least be honest about it! Like I was! Of course it was going to be painful! We're your friends! We're your nakama! There was no way your leaving us wouldn't effect us!"
He glared a hole into the swirl eyebrowed cook. "You know how Luffy is. When Vivi tried to do the same thing, fight so no one else got hurt besides herself, Luffy called her out on it! And you, you agreed with him! How could you possibly think, two years later, that he would be okay with you alone being hurt?"
Usopp was panting, his eyes blurry with an inexplicable wetness. A loud, growling stomach threatened to cut into the moment but a quick glance Luffy's way revealed he was still staring out at the sea. He was lost in his own mind, trying to find the way to let them go, to give them freedom. That was the kind of captain he was; stupid, but loyal to a fault. He would destroy himself rather than take away their freedom, their independence. He pointed at his beloved captain, tears raining down the sides of his face.
"You guys don't get to judge! We all put him here, in this position! No one here can get through to him, no one here knows how to help him! It wasn't just one person who backed him into a corner! We all did it."