This blatant absolutist statement is completely false. It exactly means, that there is no computer which is secure today. It also means, that it’s pointless to care about security on any phone in existence, because it cannot be achieved that currently.
Moxie believes in security above everything even if it takes choices away from the user and forces you to trust a third party (in this case him, but also the mobile vendor and Google because he doesn't trust custom firmware either). Basically what he calls the mobile security model. And the reason I hate mobile devices with their closed model and attestation crap to make sure I play by the vendor's rules.
I believe a user should always have the final say in everything. If the user makes it insecure that's their business. Basically the desktop security model. And the reason I don't like working on mobile devices if I can avoid it.
I'm as principalled as he (and other people like him) is so I wouldn't even enter an argument, there's no point.