I wish they DID “research” it — and the answer orbits around John 3:16 and makes no categorical imperatives about flags.
If someone had actually worshiped a country or its flag and then became a Christian and it hurts his conscience to keep on saluting the flag, then he shouldn’t salute the flag or be pressured to do so. But this is a situational accommodation to a weak believer.
What a chap like Kaepernick is doing with respect to the American flag, pales before the question of what he is doing with respect to Christ (and currently he is pledged to Allah IIRC). Let him diss the flag if he believes that is right. But please do not diss Christ forever.
Kaepernick is a gullible idiot, if he thinks he is actually conferring a benefit on those with whom he claims to identify.