<<The aim of the school must be to give the pupil, beginning with the first sign of intelligence, a grasp of the notion of the State (through the study of civic affairs).>>
The best argument is to tell those against that if they don't like it, don't recite it. Tell them to just sit there and keep their mouths shut while the kids who love their country do recite it.
Some good things to bring up would be how your time would be better spent in English class. More specifically, becoming acquainted with the apostrophe and its uses.
I'm afraid that if you were chosen to debate the motion and have to SUPPORT the Pledge then you basically got the end of the sick that they poked the dog-poop with, not the end they were holding!
Fundamentally, the Pledge is"unAmerican" on almost every level; it's a vow to defend an inanimate object!