"[i]charm person[/i] specifically states that the [i]charmed[/i] person retains his own will and must be convinced to do things. Further, even Helpful characters can still hate your guts, and [i]charm person[/i] only puts you in "friendly" territory.
In the middle of a battle with goblins on all sides, the goblin wizard casting [i]charm person[/i] on the fighter can expect the fighter to try and subdue him and the other goblins rather than kill them, but he'd have to be a heck of a diplomancer to convince the fighter to actually switch sides, turn on his allies, or even just stop fighting.…