I don't agree but why would you call it a religion?
Because it looks like a religion and quacks like a religion.
Substitute cross for flag.
At all sports games everyone rises in honor of the US cross which represents the parcel of land they were born on. They then recite their pledge of allegiance to the cross. Those who don't believe in the US cross are still pressured to pledge allegiance to the cross or they live in fear of ostricization.
Interestingly, this practice is common on basically every inhabited parcel of land in the world, where the occupants are loyal to their local cross, because each one believes their cross is the greatest cross.