There may well be cases where having differing opinions between flight crew members resulted in a crash/hull loss/etc, but that doesn't mean that we should never have two pilots. People are always quick to point out where pilots have made errors, but what we don't hear about is how many times having two pilots *avoided* an accident - ie where one made an error that was caught by the other. (The same argument applies for wanting pilotless aircraft - where the aircraft couldn't handle a situation/suffered failures/etc and one or more of the pilots saved the day). A bit like the old 'where do we need armour on our warplanes?' story. People are quick to say 'where all the bullet holes are!" or "pilots cause (X) number of crashes" but the reality may well be 'where the bullet holes *aren't*" - 'pilots prevent (Y) times MORE crashes'