James: Is the primary reason for the objection political (because it expresses allegiance to the United States)? Or, is it religious (because it makes the passing remark "one nation under God"?
If you're looking for the underlying reason, I'd classify it as primarily ethical for the collective reasons outlined since the beginning of this thread.
Why should my child be pressured to make a pledge that does not reflect her own convictions in the first place? To instill some sense of national pride? As one humanitarian put it, "If our country deserves the respect of its citizens, that respect should be earned and freely and individually expressed. If we need to bolster love of country through semi-coerced oaths, something ain't right."
Six: And pledging allegience to the flag is whatever-the-hell the individual pledger thinks it is.
So if the pledge is both ineffective and meaningless, I can't help but wonder why its part of my kid's school's morning routine.