Oh, the answer really is “let everyone go,” and then “get rid of all billionaires, cap wealth at $100,000,000 and tax the rest at 99%, and make sure every single person has a high-quality, safe place to live, good food, medical care, and friends.
Less, much less, but not zero. You'll always have the odd person who ends up a problem even under optimal circumstances. The range of trait expression in humans is very broad, and there are a lot of humans. You can't run away from that, but you can be compassionate about it. Insisting that your socialist utopia will simply render all humans happy and harmless, and as such there will be no need for forceful law enforcement is obviously wrong and harmful to your movement.
Suddenly there will be far less crime.