Story time

My nephew, who is around 15 years old, has gained knowledge about bitcoin and cryptocurrencies through exposure to discussions between his father (my brother) and me, as we frequently talk about bitcoin. Whenever he has free time from school or chores, we allow him to listen in on our conversations and ask any curious questions he may have. For instance, he often asks questions like, "Uncle, what is bitcoin?" or "Is it a type of currency? Can I have one?" We do our best to explain the concept to him, but sometimes he grasps it easily while other times he struggles to understand. What I do know is that this young boy is displaying a keen interest in the subject.
Recently, he expressed his frustration about his teacher and classmates labeling bitcoin as a ponzi scheme or a scam each time he talks about it. I'm seeking a variety of advice that I can offer to my nephew in this situation. Although his father suggested that he should stop discussing bitcoin, I don't feel comfortable with that approach. What are your thoughts on this matter?
In a situation like this; you need to go into the perspective of the teacher and the classmates. If you continue to be on the defence with regards to bitcoin; then you will not be able to change the narratives in the teachers mind or after thought.