What makes you think that this will reduce violent crime in any meaningful way? The guy who mugs you isn't going to go on Messenger and send out a quick "brb gonna mug someone" message. And they definitely won't if they know the government is listening.

And regardless, we trade freedoms for risk of death all the time. We would have far less crime if no one was allowed to leave their house without an ankle monitor and a body cam, but that would be a violation of people freedoms.