The reason speed limits make such a great example for these arguments is because they're a preemptive law. Technically, nobody is directly harmed by speeding. We outlaw speeding on the belief that it statistically leads to and/or is correlated with other harms. Contrast this to a law against assault or theft: in those kinds of cases, the law makes the direct harm itself illegal.
Increasing the precision of enforcement makes a lot more sense for direct-harm laws. You won't find anyone seriously arguing that full 100% enforcement of murder laws is a bad idea. It's the preemptive laws, which were often lazily enforced, especially when no real harm resulted from the action, where this all gets complicated. Maybe this is the distinction to focus on.
Increasing the precision of enforcement makes a lot more sense for direct-harm laws. You won't find anyone seriously arguing that full 100% enforcement of murder laws is a bad idea. It's the preemptive laws, which were often lazily enforced, especially when no real harm resulted from the action, where this all gets complicated. Maybe this is the distinction to focus on.