The value of Bitcoin will only reach zero if it is irreversibly hacked. If someone finds an absurd flaw in the protocol.
Otherwise, it will always have some value since it is a solid project and with great utility. People who have not bothered to study the protocol try to give crude hints like this.
Technically, the cryptographic algorithms used in Bitcoin are safe and secure, but its price depends on the balance of supply and demand. Any coin follows the trading rules and tactics on the crypto exchange markets. I see that Bitcoin looks good compared to the alternative crypto currencies which plummeted down dramatically. Currently BTC costs $6300 and it has not yet fallen this September. I don't believe that Bitcoin will hit zero. Moreover, investors support this crypto currency very strongly at the level $5900.