Given the long-running outrage of fingerprinting all visitors on arrival, photography as well seems pretty trivial in comparison.
And I'm also having some difficulty with the idea of portraying it as "invasive biometric scanning". A photograph is hardly the most invasive thing you expect to happen when you pass through an airport.
Kudos at least to the gov't for finally admitting that there's no (legal) way to treat foreigners and citizens at the border any differently. It'll take time, but one day I expect the message will eventually percolate the American consciousness that they are not immune - anything they can do to us aliens, they can do to you citizens too.