That's wonderful if the crime is something clear-cut like murder. We can generally all agree that it is unethical and worthy of punishment.

What if it's something we can't quite agree on, or tyranny of the majority? Joe McCarthy happened once, and he didn't give a shit about ex post facto. Presuming someone like him will never come along again is a road to pain and suffering.

Spend ten minutes reading about what Crypto-Judaism is and why it is even a thing. Then look at abuse of power (I've known 2 people who have had LEOs as stalkers). A big part of warrant law is the premise that you don't give people information they don't need 'just because'. Very similar to the computing concept of Principle of Least Power. They prove they need it, you give it to them, but not a moment before, because who knows what they'll get up to.