This isn't an opinion or a belief, it's a verifiable fact. We know the world is round because: if you travel east you'll eventually arrive at your starting destination; if you stand on a ship's crow's nest you can see further than the crew on the deck because of the curvature of the earth; if you fly a plane and make two 90 degree turns and travel an equal distance, you will end up at your starting point due to the curvature of the earth; if you go to space in a space station, you can visually verify that the earth is round.
Cargo culting acolytes will believe the earth is round with no explanation as to why. Just because you believe the right thing doesn't mean you're not cargo culting. If you can't explain why you believe what you believe, you're simply believing to follow a particular crowd, regardless of the validity of the belief.