An argument could be made that no christian, jew or muslim should stand at attention for the flag or the anthem.
“You shall not make for yourself a carved image, or any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth; you shall not bow down to them nor serve them. For I, the Lord your God, am a jealous God, visiting the iniquity of the fathers on the children to the third and fourth generations of those who hate Me, but showing mercy to thousands, to those who love Me and keep My Commandments.