Some quotes from the LBBs:
Men & Magic, p. 26:
Protection from normal missiles
The recipient of this charm becomes impervious to normal missiles. This implies only those missiles projected by normal (not above normal) men and/or weapons. Duration :12 turns. Range: 3"
I hadn't noticed the reference to normal men there before Cooper posted it on the OD&D forums, but I did notice it in the entry on Berserkers.
Monsters & Treasure, p. 5:
BERSERKERS: Berserkers are simply men mad with battle-lust. They will have
only Fighting-Men with them as explained in the paragraphs above regarding Ban-
dits.They never check morale. When fighting normal men they add +2 to their
dice score when rolling due to their ferocity.
There's been some debate about this reference to normal men, whether it means what AD&D referred to as "level 0" or whether it should include Fighters up through 3rd level. I think it means "1 hit die men with no special powers." The support for this interpretation is also on page 5 of Monsters & Treasure, in the Bandits entry: "Although Bandits are normal men, they will have leaders who are supernormal fighters, magical types or clerical types... Hit Dice: 1 die/man." The ability to cast spells or the bonus hit point for 1st level Fighting-Men makes these people supranormal.
In fact, the cleric is practically a normal man: 1 hit die, no spells. A 1st level anti-cleric doesn't even have the ability to turn undead in the LBBs, so they are truly normal men.
The debate, then, is whether Berserkers get their +2 to attack versus 1st level Fighters, or whether this is just against hirelings. Some feel this makes berserkers no threat (although they also never need to check morale, which is pretty significant.) I think I'm willing to add a little something to make them feel more "berserk":
"Once berserk warriors take enough cumulative damage to kill a normal man, they continue fighting until they are hit twice successfully in a single round or the fight is finished."
This rule is actually re-usable for a simplified version of the Monster Manual's bears and boars, making all three dangerous. However, the original question remains: how do people feel about berserkers and Protection from Normal Missiles spells basically being useful only against NPCs?