Your argument boils down to "if people were 100% just, fair, and good, we could do this", so I'm not sure what the point of it is.

(Entertainingly, if people were 100% just, fair, and good, we wouldn't need this database... or police or militaries for that matter.)

At any rate, even if I could ensure, in perpetuity, that my DNA would not be used inappropriately (where I get to decide what that means), I would still not want it collected and database'd. People deserve to have privacy in their bodies.