The "No Fly List" is a perfect example of a discriminatory government watch list with no transparency, oversight or recourse. Not sure you wanna bring that up.American security agencies from local police to the CIA already have and use such databases all the time. Without the kind of checks and balances you say are necessary. Have you heard of the No Fly List? Most Americans approve of them and their use.
Although many made objections on specific points, lots of them the same as yours, sensible people recognized there could be away to balance non-interference and public safety. The point is to solve those issues to get a needed job done, not use them as weapons to ensure nothing's done at all.