General Mitchell: Now wait a minute! This is a press conference! The last thing I want to do is answer a lot of questions.
Pierce: Listen, Frank. We're all gonna make nice for Captain Hildebrandt today, but don't push us.
Burns: Well, a shave wouldn't be a bad start. You both look more like bums than doctors.
Trapper: Actually, I was, uh, I was thinking of becoming a bum doctor. But the proctology class was full!
Burns: HA! HA! HA!
Answer: Even an Army field hospital would have SOME weapons for self-defense if the enemy attacked. What's meant is that it's not a combat outfit, and therefore wouldn't have enough weapons to actually attack anyone. (It's also mentioned a few times that the Officer of the Watch is supposed to carry a pistol at all times, but Hawkeye refuses to do it when he's in charge and Colonels Blake and Potter don't enforce the rule).
Captain Defenestrator