Northern Phoenix
Adventurer
It's not "old-fashioned," it's not "a PVP style of mentality," and it's not a "gatcha," it's just a kobold with a crossbow. It's the same crossbow that the barbarian can purchase in any shop and use without penalty, but decided not to because it wasn't optimized and therefore, "completely useless." The player made a deliberate choice to hamstring his character in all ranged encounters--you can't put that on the DM.
It's pretty silly for the player to assume that because he decided to never buy a ranged weapon, ranged combat is now off-limits. (I mean, what if another player wants to play an archer ranger? Is he just out of luck now?) Likewise, it's pretty silly for the player to assume that because his wizard focuses on fire spells, all enemy spellcasters can't cast the protection from energy spell.
It's a disconnect alright, but I think it's in the opposite direction from which you implied.
A kobold won't have a crossbow unless you want him to for some specific purpose. A enemy caster won't have "protection from energy" unless you want him to for some specific purpose. Simulationism is an illusion, in reality the only things or facts that exist outside of the player characters are what the DM decides exist for some specific purpose.