If you can get star trail pictures from different points on the Earth then the only explanation of what is being seen is that the photos are taken from a globular Earth.
It's a little convoluted, but convincing if you draw a circle, put two dots on it and think how would we see the circular paths we see from different points on the Earth if it were flat.
One thing I learned from arguing with a deranged wife is that the hardest thing to prove is the obvious. Further, if you ignore the math you can believe literally anything.