Had a similar experience around age 10. Learned that cucumbers generally have a higher water percentage than seawater, 97% to 96.5%. Tell that to a friend of the same age, he says that can't be true because all the oceans have more water than all the cucumbers in the world, we begin debating and then start fighting about it and a teacher comes by to stop us and asks what's going on. I explain and the teacher immediately looks at me like I've lost my mind, pulls my friend to the side and asks him to leave, takes me to a room and sits down to try to explain how I'm wrong and that I can't start fights over things that anyone can prove is untrue. A week after I'm sent to a kind of mental health meeting, she immediately understands and looks it up, sees that I'm right, tells me to keep away from talking about "stuff like that" with friends and others my age and also teachers and parents of other kids because it doesn't matter if I'm right or not, just that I have to think about how others perceive me...
I'm not still mad about it, but can't deny that it feels wrong and weird.