The easy way to make them see that bitcoin isn't a scam is whit the market capitalization
I am not sure market capitalization can make them understand and not think negatively about what we explain.
I just wouldnt want to explain to them in detail if they never had the belief that bitcoin is something special in this era. Explaining it will only waste time and not make them sure.
I deliberately introduced bitcoin to a number of people who had never even heard of it, even though it was only a name. But I was quite surprised by his reaction, they were just afraid I was directing them to illegal and infringing things and they were also afraid that I was trying to enrich myself with their money. Because of this, I no longer want to explain intentionally to anyone but those who ask first.
~snip
So, instead of trying hard to convince them, try to make them see the advantages in it. Let them understand the whole concept themselves.
It would be better to encourage them to find out more about bitcoin by giving them a reading reference. I think it will be more beneficial for them, and we dont need to bother convincing those who have different perceptions because its like we are talking on the wall.