Bitcoin is ultimately computer code. It is hard-coded so that no more than 21 million coins can ever be created. True value in a currency is created by scarcity: when we had a gold standard, value was based upon the fact that gold is a rare metal.

With Bitcoin, because the code says that no more than 21 million will ever be created, we will reach a point when all of those coins are in the hands of SOMEBODY, and that means that anybody who trades in Bitcoin will be trading in the value of an increasingly rare resource, meaning its value will only continue to increase and improve the wealth of all who hold it in the process.

At least, that's how I'd explain it... I'd also be sure to explain how KYC ruins all privacy and ownership aspects, as well as the fact that it's certainly not a perfect solution and I wouldn't claim it's unstoppable as some do.