Yeah your d.m. laid some plot wagon tracks. At least by what you describe. The g.m. should never choose which way to do something is right for the party.
If these people are about to be massacred and won't lift a finger to save themselves, then that is natural selection at work there.
It's horrible, callous, and cold to say... But even in nature prey has the instinct to avoid the predator. These people with "their higher moral code" are choosing to buck that very obvious trend.
If these men won't protect their families, if these mothers won't shelter their children elsewhere then that is their fault not yours.
So unless the villagers knew something that you do not (an ancient gold dragon watches over them for example) you did do the good thing. You saw a need, you offered aid at great risk to yourself, you asked for nothing in return because helping is its own reward.
They refused your help.
D.M. with an idea but poor execution of that idea.