With both people's consent. There's 100% a problem using violence to stop this.
It's only different if someone does it without consent.
No. How is it morally different than other plastic surgeries people get, which make one look absurd (like Madonna?). Take Blaire White. She's done all the surgeries but the bottom one, and takes horomones. Which of her surgeries was immoral to you, and why isn't it immoral for a woman to get the same surgeries, and then on what moral basis should government step in to stop this?
You are protecting no one's rights when the government stops this. In fact, you are violating them. You are violating someone's ability to choose what is done to them, and violating another's right to work (do consensual surgeries) without government interference.
What you are proposing is simply a nanny state of the Right, despite your supposed belief in limited government.
And this is why 'pure' Libertarianism will never be a meaningful political force. You do not seem to be able to comprehend that it is
inherently good for a person to have a healthy, fully-functional body, and that anything that violates that is to at least some degree
bad, even if different levels of it can be justified for different reasons.
Further, you seem to be completely unaware of the problem of people being coerced into giving 'consent', corrupt members of the medical establishment who make their money doing certain things lying about it, and the root problem of
if you are insane enough to want to mutilate your body for no good reason, you are not sane enough to give consent for someone else to do so.
If someone has ownership of their body and gives consent to someone else to destroy their property how is it a problem. If I went and hit your car with my baseball bat I would be violating your rights. But if you said I could then it wouldn't be a crime. Your standards of "limited government" are inconsistent. I mean if you were consistent you would either go with Abhorsen's libertarianism that let's them do it as it's completely their choice, OR you'd go with a more traditional Christian approach of where you actually don't have ownership of your body it's more like on loan from God. Same reason why Christians oppose suicide.
A human body has an inherent moral value that a car lacks. I'd still say it's a minor moral failing to damage a functional car for no other reason than a fit of pique, but not something the state should get involved with.
My standard of government is quite consistent. I don't go with Abhorsen's libertarianism because it is blind to reality. I do hold a Christian standard, because God has given us stewardship of our own bodies. That's part of why physical self-destruction is not moral, but because I have stewardship of my own body, I can still do so if I wish.
On the whole, 'it is acceptable for a doctor to
help a patient self-harm' is a terrible door to leave open, fraught with massive abuse potential and perverse incentives. And that's
before we get into political types using this open door to push for various undesireables to be given 'treatments,' such as what some people on this forum like to talk about with lobotomization having once been considered a 'treatment' for homosexuality.
And this is also wrong? Again, if the person is otherwise sane, just hates there left leg that much, then sure, why shouldn't they have the right to have it cut off, if they can get a surgeon to agree to do it? It isn't your business.
There is moral good aside from 'free will.' There are multiple different moral values that exist in tension with each other, and your apparent failure to recognize this is indicative of why pure libertarianism is so culturally weak.