It seems to me that you entirely forget the characterization of Santa Ana and the Mexican army in the John Wayne movie. You must know that Wayne deeply respected Hispanics, to the extent that he kept marrying them! In his movie, Santa Ana is shown as a dictator, but much more chivalrous than he actually was. Nothing about executing the few survivors and burning the bodies, for example.
As far as the soldiers were concerned, I remember the scene where some of the Texans are talking about how they respected them, that they 'felt proud of them even while' they were killing them, that it 'speaks well of a man' that he would be willing to die for what he thinks is right. I guess this means that John Wayne is just too PC for you.
And bad acting in a government created historical recreation, I am shocked, shocked, I tell you!