First, there's the point about the military needing to be absolutely confident that an officer will tell the truth, especially in combat situations, and the saying "If he will lie to his wife, then he will lie to you too". Military people need to be trusted. They are entrusted with vital secrets, and millions of dollars of equipment (and occasionally nuclear weapons). If they can't be trusted, then the military has a problem.
Second, it's obvious that you are a woman, and have never been in combat. Otherwise it would be obvious to you what the down-side is of somebody finding out you've been screwing his spouse, at a time when that person has LOTS of opportunities to arrange your death.
What absolute horse manure. People lie to their families all the time.