I think it's the idea of making kids recite the pledge every day and the uber-patriotistic tones of that idea. Think about it, making a bunch of five year olds, everyday, recite the fact they are American, sometimes under threat of consequence, can seem really messed up when looked at from the outside.

"boo hoo, they make kids say some silly poem to a flag" said a person who probably grew up in suburban america, not knowing how easy they had it.