I'd have more sympathy to the "we need to be able to read every one's message, and open up everyone's communication to criminals to stop crime" story if there was any evidence it would actually do anything.

There is no evidence that the reason terrorist attacks (the common go to) would be stopped by removing encryption from people, because we know that existing attacks have occurred even when law enforcement is already aware (take the Manchester bombing: multiple friends and family had reported him to the police on multiple occasions).

We do have a huge amount of evidence that any such attack on privacy will immediately be abused. In the UK those laws that were passed to "stop terrorism", etc are used to catch people not picking up dog poop, not paying TV licensing, etc. In the US we had wide spread warrantless surveillance of literally everyone, courtesy of AT&T.

My opinion is that any law that proponents proclaim will only be used to stop X should contain terms along the line of "any use of this legislation for any purpose other than X invalidates this law, any evidence acquired must be destroyed, and any convictions derived from such evidence are no longer valid". I would give good odds that any attempt to add such text would result in push back by the people saying the law is only needed to stop X.