I don't think there's anything to stop you attacking specific objects with a ranged spell(-like ability). You can use telekinesis to disarm someone, and I don't see that TK should be treated as a special case in this regard. That said, I really dislike this sort of thing, if done on a regular basis. It smacks too much of called shots ("I shoot the giant in the eye, that'll kill him no matter how many hit points he has!").