It is far, far, far, far more likely that this sort of mass surveillance capability will be used for bad purposes (even by law enforcement) than it will be used to find an escaped child murderer. (Hell, I am convinced that this sort of thing is already more frequently used for bad purposes than good.)

Also like, how many escaped child murderers are there per year in the US? Like... one? I don't think that's worth pervasive mass surveillance, though I would understand how a parent whose kid had been abducted might believe it would be.