Several "hard" drugs are designed to put users out of their right minds and into a state where they're more likely to hurt others. Same with alcohol, which despite its long cultural history, mainly serves as part of a socialization ritual and could be replaced with something else that's not as harmful. Perhaps we should try prohibition... again?
Cars with top speeds above 85mph are designed specifically to do something (in the USA at least) that society deems harmful. Number of cars ever driven at high speed on tracks or long private roads is minimal and not relevant.
Self defense and hunting are valid reasons to harm other[ creature]s. It does not follow that something should be banned just because it's designed to harm others.
In terms of what various things are designed to do, relative to what society considers acceptable, it makes more sense to keep guns legal than to keep fast speed-limit-exceeding cars legal, or to legalize hard drugs.
- Drugs: Not designed to be harmful. Can be dangerous.
- Guns: Designed to be harmful. Can be safe.
I'm not saying that you can't argue that drugs are so dangerous that they should be prohibited or that guns can be safely used and should be allowed. The topic is the same but the starting point is not.
Your examples are of things that are dangerous, not of things that are designed to be harmful.
What does their being designed by humans to be dangerous and hurtful have to do with anything? Is it not allowable to hurt others in self defense? Is it not allowable to hurt animals for food?
There are other things that are hurtful and dangerous, and whether something is designed that way by humans or not has no bearing on the utilitarian calculus. Particularly so when there's no categorical imperative against the thing they're designed to do (unless you're against all self defense and hunting).
> Is it not allowable to hurt others in self defense? Is it not allowable to hurt animals for food?
I fail to see how such general and silly questions foster a debate. No one said or implied those.
> has no bearing on the utilitarian calculus
That's why we need to (wait for it) debate!
> no categorical imperative against the thing
You know what's the problem of the categorical imperative? It's very subjective.
You know how we overcome such subjectivity? (wait for it) debate!
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My point is simply that in one the harm is direct (designed to) and the other is indirect (can be used to). Due to that the debate between those should be different.
Much more meaningful to compare hand guns with explosives and other weapons, and drugs with alcohol and generally self-harm.