Replace "chat" with "speak", and suddenly it is trivially obvious to everyone how horrific this is:
> If we don’t hijack privacy in speech, how do we fight crime happening in private conversations? If [the] government doesn’t have access to what you say at home, what’s stopping criminals from using their homes and never getting tracked down? Or proven guilty, since all the proof was said behind closed doors? Aren’t we hurting ourselves by being so obsessed with privacy?
Should we be obsessed with privacy, or should we let the government put microphones in every house just in case there are paedophiles talking about their sex acts and hence getting away with it?
Similar arguments can be made by substituting other things that were traditionally considered the domain of only authoritarian dictatorships, such as opening all letters and reading them before they're delivered by the postal service, or keeping tabs on what books you borrow from the library.
I grew up in one of those countries, and I can tell you that it's not at all nice that they tracked what you photocopied, you know, just in case you wanted to print out anti-party ("one" party!) propaganda... I mean... something... something distributing child porn. Yeah, that's it. That's the reason.