Desertion: Leaving or running away from service or duty without the intention of returning. There was a war going on at that time, and that was the rule for cowardness. I dont recall the "outcome" of any court marshal saying Custer was AWOL or Deserting.
Agin, It is so easy now days to be so PC and stick up for the Savage Indians of that time, and that's what they were. That's History Not Political correctness. But if it gives you a warm and fuzzy feeling,...Then feel free to Run our Military Hero's down... Could be a feather in your cap.