Seriously, he utterly misses the point. Signing A records and so-forth provides very little in the way of end to end protection, true, but what it does provide is a trusted, consistent mechanism to place security information (public keys, certificates et c) which end-to-end services can use to secure those services, without having to involve third parties in every single deployment.
Basically, think of it not in terms of security for the DNS but as security information provided through the DNS.