Scams are easy to detect because if you dig down thoroughly, you will definitely find out what makes a thing a scam, but Bitcoin is not a scam. If you dig down the history of Bitcoin thoroughly too, you will find every reason to believe that it's not a scam. So, to convince someone about Bitcoin, kindly crack down on the history of Bitcoin with those people by telling them the reason why it was created, the purpose it's serving, how most people have trusted it, and the risks involved. If it's really some that have interest in joining the Bitcoin space, they will do some digging themselves, and when they do, they will likely want to invest.