By "cash", I think he meant paper money transactions. If that is the case, then yes, you can't reverse cash transactions. Only if that "cash" is stored in a bank account, and sent to another person from there. That's because the "cash" is essentially "digitized", allowing a middleman to easily reverse the transaction if something goes wrong. Same goes with credit cards.
But with Bitcoin, it's another story. It's more akin to cash, because transactions are completely irreversible. The only way to "reverse" a transaction would be for miners to reach a consensus and rollback the Blockchain. And that's practically impossible to achieve. Therefore, people should be more responsible when using Bitcoin to avoid getting scammed or sending coins by mistake. As long as BTC stays decentralized forever, there should be nothing to worry about.