As far as I can tell in this discussion so far no one has equated the moral problems with a cause. And you are correct usually moral is a product of leadership. And in this case both the leadership of a commanding General and a President. But a part of leadership is the responcibility of taking care of your men and NOT using them wastefully or dangerously. Which goes back to the original question of why Meade did not immediately pursue Lee retreat from Gettysburg and suffered Lincoln's scolding and his demand for an explaination of Why Meade didn't press Lee.
Burnsides moral problem was because of the his wasteful use of the army in those repeated hopeless assualts against Mary's Heights. Those attacks became the defining element of that Battle even thought there was an entirely seperate battle going on against Stonewall Jackson troops on the Confederate right, at the same time, which were much more successful.
Meade inherited an Army that had suffered the defeat of Fredericksburg and Chancellorsville with the moral problems that were engendered by those defeats and the replcement of a commander, in Hooker, that to some degree they respected almost as much as McClellan. I wonder just how much faith Meade had in his armys abilities to press an attack at that time.