I have debated that with other people. If you have important evidence to solve a crime like that (missing children is a great example), the best thing to do is

I have debated that with other people. If you have important evidence to solve a crime like that (missing children is a great example), the best thing to do is give your evidence to the police in as anonymous a fashion as possible, and also try to give strong signals that the evidence is credible. The complaints people have with the system is that it incentivizes silence. I think most people don't advocate "don't talk to the police" because they want to see innocent people harmed (as in your example). It's precisely because they don't want to see innocent people harmed by police whose incentives, frankly, don't match up with "trying to find innocence".