Earlier quoted context omitted.
Are you conflating DoS (something a firewall can deal with) with the kind of hacking that can penetrate a system? I'm not sure a firewall can do anything about (for example) SQL injection.
I think commenter is describing his company's operation, what attacks they were facing, and that listening to advice countered them. Commenter doesn't mention a SQL Injection or claim his case applies to anything else. Instead, merely points out that listening to professionals who understand risks of your technology and following their advise can prevent problems caused by those risks. That was my take.
Penetration isn't quite as easy.