Repeat after me -
"I have promised myself that I will be focusing my time and efforts on building my own future instead of trying to convince someone who makes the fashionable mistake of labelling everything they don't understand as scam."
Sometimes trying to convince people, especially the ignorant ones is just a waste of time. The more effort you put to dispute a wrong view about a project, the more they proudly exhibit their lack of knowledge. Some of these negative views are born out of a lack of information or bad personal experience. It will be very difficult to convince anyone that has been a victim of a shitcoin scam that Bitcoin is not a scam. The negative experience has affected their sense of reasoning.
...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...
One of the characteristic features of the ponzi scheme is the promise of a guaranteed profit, which is absent when investing in bitcoin. Understanding such fundamentals can easily identify where the dangers lurk. But this is unlikely to help the teacher understand this, since he has already formed a negative image in relation to bitcoin.
People are unaware that this is the strategy to attract them. No investment can guarantee a fixed profit but these Ponzi schemes assure investors of a certain percentage of profit at a certain time. And I wonder how sure these business owners are that they will constantly make a profit. Greed is a leading factor that makes people fall for these deceitful schemes.