I'll chalk up ignorance because it is more polite.
First, any person attending the Naval academy only commits to a Navy career at the end of year 2. Anyone can leave before that date and have no commitment to future military careers. A quick google indicates that roughly 20% do for various reasons. So knocking Gilman for leaving prior to year 2 is just stupid. Lots of people do it. It doesn't matter the reason.
Second, the Navy, AFTER GILMAN BEGAN ATTENDING, changed their rules about when grads could play pro football. Old rules, you can play pro football right away, new rules serve for 5 years first..which in this day and age essentially eliminates a pro football career. For example, under the OLD rules, Gilman could have played in the NFL immediately and fulfilled his military commitment in alternative ways. For example, Keenan Reynolds (graduated 2016), upon graduation, was able to play in the NFL (and still is) and serve in the Naval Reserve or in other ways to fulfill his 5 year commitment. If Gilman discovered after one year at Navy that he didn't see his future in the navy and that may have been because he loved football more, he isn't any different that 20% of his fellow classmates who decide that their future isn't in the Navy.
As for the total hypocrisy of the NCAA, it has essentially okayed players to change schools for a variety of goofy reasons (many of which are directly related to impacting a kid's pro prospects) without "penalty" like the school going on probation, a coach leaving, one idiot (who was thrown out of the school) yelling a slur from the stands, etc etc, is okay while a school changing it's rules (after the fact) directly affecting a future career choice is not okay.
How is Gilman's desires for his future any different than Josh Fields or Shea Patterson (among others) whose sole and only reasons for transferring were football related?