first of all if you have to experience pain to experience pleasure or vise versa, how could you ever experience either until a magic moment when you expeirenced them both at once? the whole notion is idiotic and reeks of blind ignorant myth making.
second, I find most of them saying that if God prevented things, we would have no freewill.... which I find another load of crap. even the bible does not exempt people from warning others if a danger exists and punishes them if they do not warn and someone is injured because of it.
if any father today discovers his son is about to go to school and blow away a teacher or other students and does nothing to prevent it, he will not be given any slack for his concern in preserving his son's free will. and no one will think him a good father and roll model.