Maybe the parents were glaring because their sons are supposed to belong to the Boy Scouts of America, a country not noted for a tradition of centuries of kilt wearing. Possibly they were glaring because they believe that the purpose of the Boy Scout uniform is to give the boys a sense of equality regardless of economic or social status. Then again it might just be that they were glaring because they perceived some sort of "favoritism" was being shown to the boys in kilts. And ya know, some parents just aren't happy about any sort of proselytizing being done by the adult leadership of a Boy Scout troop, and that could have accounted for the glares you received.

Then again, they just might have wanted to go home.