Doesn't make sense why they got all squeamish about killing banditos at the camp

When the banditos rode into their camp and were all exposed why wouldn't they just shoot them all dead? Dobbs and Curtin were laughing about who killed more during the train attack and only minutes before Dobbs, Curtin and Howard were going to murder Cody in cold blood, but they all got squeamish about killing all of a sudden allowing them to take cover behind the rocks. Of course it was really to help the plot so the federalalies could chase the banditos away, so Dobbs would meet up with them again on the way to Durango. Scenes like that make this movie from being as good as its reputation claims it to be.