I see Coby as the sensible marine, what he though was confirmed in Smokers face, something went really wrong, they would just end up wiping eachother out. Anyone who thinks WB pirates were simply going to be wiped out while running needs to read the chapters again, the commanders made stand, and the rest of the pirates were still killing marines. In the end marines would have failed to saved the living marines that died slowly, 1 pirate alliance would be destroyed, marines would be destroyed, and BB would have laugh. Oh and chances are Shanks would have different view on things if he came and all of the pirates were dead, including luffy.
Edit: Since Shanks arrived and Akainu didn't get to finish Curriel, I'm confident the commanders will take care of him like Joz.