I agree, that statement is pretty demonstrably false. Even Tor hidden services have weaknesses as we've seen recently.

At least with anything concerning privacy and security, radical honesty is the best approach. Most people realize nothing online has perfect security or anonymity, you just need to make the case that you have better security and anonymity than competitors in the space. Lots of companies (particularly SaaS providers) make grand claims about their impenetrable security, but only foolish people believe that nonsense.