My oldest daughter was sent home from school once for wearing an orange scarf her grandmother gave her. To her it was just an accessory. To the school authorities, it was a possible gang marker.I made the decision that she would not wear the scarf to school - not because I agreed with the school, but because if wearing orange marked her as a gang member even though she wasn't, I didn't want her endangered.
I repeat, an accessory is not free speech, it's just a scarf (or necklace). And I don't think it's a "Hate America" move, considering that they apparently did not have a problem with the girl's shirt.
...now, if there was a cross hanging from her necklace...