It's only part of the premise, not its entirety. A large part is a sense of justice, or ideology, that tempers the pragmatism, and acts as an instictual signal that a law might be harmful in the long term.

Compare it to the 'do no harm' in medicine: say a doctor kills a healthy patient, so that his organs can save five others. At first, many lives are saved, but when this becomes widespread, how long until no-one dares come near a hospital? Or how likely is a patient to admit to having suicidal thoughts, if it results in police going through their private home, confiscating guns, or even committing them for their own good?

Absolutist, 'ideological' positions such as do no harm, and doctor/lawyer-patient/client confidentiality, are important guards against unwanted second-order effects.

It depends on the law. Take the fourth amendment. It doesn’t prohibit searches and seizures. It only prohibits “unreasonable” searches and seizures. Or the fifth amendment. It doesn’t prohibit depriving someone of life, liberty, or property, but permits it subject to due process.

Other provisions are less loosey-goosey. The first and second amendments are categorical prohibitions. You can’t establish a national religion even if you think the results will be tremendously beneficial. The taxation clause is similarly clear. We needed an amendment to create the income tax, even though it was necessary to a modern state.

Correct, with everything from speed limits, to smoke free areas, to dumping out toxic chemicals on your own land.

I'll never understand how a significant amount of the population can entertain the idea that "gun rights" are central to liberty, or that unlimited liberty above long term survival of the species is somehow desirable.

Because th long term survival of our species does not depend on gun control. Mass shootings kill few people relative to just about anything. All deaths by rifles and shotguns are still fewer than those by blunt object. We could allow hand grenades and rpgs and still survive as a species. We are harder to kill than roaches. All that said, I am in favor of limiting the number of gums per month that can be purchased to slow mule purhases. And expanding unrecorded background checks universally to the point I can/must do one on my phone if I want to do a private sale.