Exactly this. Police in most countries can search your home if they have proper legal justification. That is extremely invasive, but it is allowed by many societies because they recognize that invasive searches with proper oversight can bring around greater liberty, if such searches catch individuals who are harming others.
As I see it, the issue is not that these websites are being used by law enforcement, but that there is not formalized rules for doing so, nor is there transparency in how they are used by law enforcement. An example of a formal rule would be a warrant requirement.
I would gladly move to any country that did not have this police ability in a heartbeat. There is no level of security that can justify to me anyway, even the most mundane aspects of our policing activity.
The problem is that police don't actually make anyone safer, they simply create order for the state after something has occurred. I have never once called the police and had them actually do a single thing to help or solve the problem I was facing. Yet I can recount countless instances of them harassing me for nothing? Why is that? Maybe the fundamental notion of 'secure vs liberty' is flawed if we aren't actually provided with more security.
I've had a fugitive apprehension team surround my home... guns drawn, riot shield, the whole nine yards... looking for the guy who broke into my home, stole a firearm, sexually assaulted a person living there, and had continued threatening the victim via phone calls and texts for months.
After they caught the guy, I found out that those guys showed up due to a DNA match against subsequent violent crimes, for which we were the only victims who knew his identity. Soon after the cops re-victimized us they put out a media alert that quickly resulted in someone turning him in. It was two more months before anyone told us they'd caught him. Two. Friggin. Months. Of continuing to worry that this criminal might make good on their threats of doing further harm.
Seriously, I can't imagine many people reading this have lived for months under that level of stress and fear.
As I see it, the issue is not that these websites are being used by law enforcement, but that there is not formalized rules for doing so, nor is there transparency in how they are used by law enforcement. An example of a formal rule would be a warrant requirement.