[Cadsby]

Fingerprinting has negative connotations for many. It's typically associated with criminal behavior, as those are mostly the only people afforded such treatment. Not commenting on whether it's a valid practice which should continue, but it's easy to see why people, who as far as they're concerned have done nothing wrong, object to be treated in such a manner.

Also, there's the usual concerns about any state entity (particularly a foreign one, which the US is far as foreigners are concerned), amassing large amounts of biometric data. It's a black box which you can't see into, have no assurances how that data will be used, who can access it, etc.