Continuity mistake: As Hawkeye writes a letter to his dad, he says "Christmas, here in Korea, as with you in Vermont, is soon upon us." Later, his dad is in Maine, and has lived there all his life.
Continuity mistake: Frank hits the pole supporting the center of the tent, which lets the tent collapse. However, in later episodes, the tents, especially hers, has a sturdy wood frame and doesn't need a center pole.
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