Bad example. We definitely do ban carrying large knives (blade length >X), butterfly knives etc. around with you. Relatedly Germany even punishes carrying around lockpicking tools (unless that is your job) -- just carrying them.
A 5cm screwdriver is more than enough to give brain damage to someone.
A flexible extension hose like the ones that go under the sink (with the nuts attached) is perfect for knocking someone out.
A titanium tipped pen is quite good if you aim for ears, temple or throat.
A tightly rolled newspaper makes a very good blunt weapon.
Breaking/banning encryption like would have minimal benefits while exposing the whole society. Don't think that only the gov't will have the secondary keys if they decide to "only" have back doors. Anyone motivated enough will have them.
If chat encryption is banned... let's say it's not hard to reintroduce it on top of existing layers for anyone motivated enough or with enough money.