You're trying to prevent my friends from fetching my email password to look secretly at my self-nude pictures.
Justin is trying to prevent my enemies from fetching my email password to gain access to my bank account and rob me of all my money.
His point is Chrome preventing the former threat, while useful by itself, can lead me to believe that I'm also protected against enemies with physical access. This belief, as we know, makes preventing the latter threat impossible. As he cares way more about the latter threat, he thinks it's counterproductive to defend against the former.
> All of your marketing screams about how secure chrome is
To be fair, that refers to being secure against remote attackers, which is the primary concern of a browser since there's not much the user can do about it by himself.