He need not rush them. How many weird weapons does he have in his arsenal that he could have used to give Robin a better shot? Considering his sniping abilities, can he or can he not have shot that grape into Sugar's mouth already (or at least tried)? He doesn't need to be some Braveheart to do any of these things, he can stand a fair distance away and do it and yet he choose to not only run away but blame Franky. Even in CP9 he was a coward but he did something. Here he's doing nothing but run. Usopp has a duty to his comrades so !@#$ his cowardice, that's not a god damned excuse. "Hey Luffy, I'm gonna leave you behind to get severely destroyed by Blackbeard because I'm a coward and that's what cowards do, we leave our captain behind." How the hell does that sound?