Upon reading the article it appears they address your concern.
It says something about how if it was someone else waiving the Mexican flag at other students they would have the same issue with it.
It sounds like the kid is a little punk who's not aruging against illegal immigration but just flaunting the American flag at anyone who is hispanic.
And, what, pray tell, is wrong with "flaunting" the American Flag??? Especially, when illegals are waving and flaunting the Mexican flag all over the place?