So my point about speed limits wasn't the issue about how some municipalities abuse them (because they can abuse any law), but about how the government itself selectively enforces them with "arbitrary" rules, and how the public itself selectively ignores them.
Unfortunately, selective enforcement of laws is a necessary problem, because benign violations of laws happen all the time. People jaywalk across empty streets,. Kids open lemonade stands for an afternoon without proper licensing or health inspections. People inadvertently walk away with other people's pens after signing something. (Malicious violations of the spirit of the law while keeping to the letter are the inverse problem, but have a different solution.) These are all technically crimes, but I think we'd all agree it'd be a gross misuse of public resources to try to prosecute them all -- and yet they're all, arguably,
malum in sec offenses. Human notions of justice are messy, situational and vague in a way laws can't be, and we've spent millennia trying to find ways to bridge that gap, from judges to juries to pardons to bills of attainder to entrapment laws to certain emergent properties of the jury system that probably can't legally be discussed in this context.
Either you selectively enforce the laws, bog down the legal system with countless frivolous lawsuits, or try to keep adjusting the laws to track with the consensus notions of justice in real time.