Nobody is saying they know more than the coaches. Anyone with a pair of halfway functioning eyeballs that has watched JC play over the last two years can see that the kid is not a winning QB, if anything he will lose games for you. There is really no argument here.
The argument is: Should someone else be given a chance? Kiffin pushed this entire "open competition" mantra and then stubbornly refuses to try another player even though the one he is playing is an complete failure. 1 good pass/4 attempts = losses. Give another deserving guy a shot. Maybe he will play better than he practices as opposed to Crompton. What's the worse that can happen, he throws a pic, the wr's aren't on the same page, the defense becomes frustrated. That all happens when Crompton plays anyways.