Not that I should expect even a little sense from right wingers, but this slogan is so messed up. Isn't kneeling supposed to be bad because it's disrespectful? So you are disrespecting the cross? Or was Kaepernick engaging in idolatry?
The flag thing is a more recent military tradition. You salute your flag and hymn like you salute your top officer, while still showing your power as a unit, not breaking a tight formation you are standing in. Kneeling down is for their enemies, our obviously good boys share the common cause.