I'll never understand how difficult people make things by not being forthright and making things awkward:
"Is it okay if I bring my boyfriend?"
"...I think there's been a misunderstanding. I had asked you on a hike as a fun first date, I didn't realize you had a boyfriend. I'm going to bow out of this, but I can give you the hike info if you want to take him." And then you laugh about the misunderstanding the next work day, and keep things at work from then on. No reason for it to get bad. Flirting is still fun! Just leave it at that without expecting anything more.
Honest answer, as someone in the military:
A LOT of military people lament how "soft" the military has become, and someone coming down on beards, fat, etc, as well as being up front with what the military is for (e.g. Department of War), scratches a whiny itch they've always had. Because every old salty sailor and sandy equivalent feels like they came from the Old Guard.
I came from the Old Guard that my peers are nostalgic about. It was terrible and unnecessarily cruel. It was inefficient and left new people floundering instead of supported. The whole thing feels like a cycle of abuse.
But back to the point, they don't care if he's underqualified, makes bad and inexperienced military decisions, or has a host of DUIs ("who doesn't?"). They only care that he's calling generals fat to their faces and getting rid of beard ememptions.