Who are these religious flat-earth supporters? Do they have a website?
As I said, a religious flat earth supportor is one who will ignore evidence when it's presented to them.
In this case we have the following problem with the Flat Earth model:
1- If light moves in almost straight paths, the morning sun would start at over 70º in the sky. This is not what we observe.
2- If light bends according to any mathematical rule, the position of the sun, the stars and the moon will not line up with what we really observe.
On a Flath earth, light can't travel in a straight line or bend according to a mathematical rule. In other words, either light is controlled by magic, or the earth is round. Whoever ignores this evidence is a religious flat earth supporter.