There are a lot of reasons why desertion is justified (and I will give 3 right now):
- The country gets involved in a war with very controversial motivation on the part of governmental decision to get involved, and a soldiers conscience makes them unable to support said war
- A policy change is implemented to the organization of the military in general, that a soldier dislikes; such as a introductions of weekly and mandatory military prayer sessions, and this conflicts with a soldiers religious beliefs
- Since governments are generally responsible for providing food to their soldiers, and are incapable of predicting what foods soldiers are going to want; they end up simply planning a pre-decided food roster to send over; and sometimes, if the government changes the roster, a soldier might no longer be able to eat the food they prefer to eat, and are used to eating
