It was a legitimate protest of a stupid law that uses a legacy of inconsistent thought and limited perception to do an end run around the first amendment, but the text of the law requires a poster per building, so if they have enough in English, there would be no "need" to accept or post them. Now, if a principal or administrator had some balls, I certainly don't see why they couldn't use one of these or to flank the posters they do post with lots of context or more diverse ideas.