I assumed they were going to evacuate the town of players before they did their luring, since worrying about NPCs over players would be stupid. You'd have to be a pretty big group of assholes if Kirito was the only one concerned about any vulnerable characters being killed in this plan.

Regarding the town-PKs, it could be possible that staying inside a town doesn't make you safe from attacks but instead makes you unable to kill another player outside of a duel. If that is true, then a player who has acquired a way to accurately launch projectiles from outside the town can exploit the code.