Well, I will admit that the argument of "de facto coercion" is not necessarily the most compelling one (the establishment clause argument has always seemed better to me), although I don't see anything particularly unsound with the underlying logic: if de jure coercion was prohibited by Barnette, then it stands to reason that de facto coercion is also prohibited. The situation is perhaps analagous to Plessy: "separate but equal" may be equal de jure, but not equal de facto. Similarly, there may be no coercion by law, but there may be coercion in fact.
Thus, the only question is as to whether there is indeed de facto coercion, and that is of course a debatable point.
I live in a neighborhood where I might be
de facto coerced from living. Certainly my choice has raised the eyebrows of some posters. Is that "de facto coercion?" In every class I attended in elementary school, I attended with a girl that was a Jehovah's Witness; she, as was her right, did not say the Pledge of Allegiance. That might have helped teach me tolerance. Permit those who wish to say it, and those people who don't wish to not say it.
