Each person has a legal right to do as he wills so long as he respects the equal rights of others and honors all his commitments. To be foolish and imprudent is to fail at self-government. Typically, people who don't govern themselves personally pay the price of not doing so. One advantage of a free society is that it focuses the costs of irresponsible behavior on those who behave irresponsibly, and it focuses the benefits of responsible behavior on those who behave responsibly. The result is that irresponsible behavior is kept to a minimum.
Some behaviors are plainly and always destructive of social cooperation.
These behaviors should be prohibited precisely because they interfere with their victims' rights to govern themselves. The precise means of deciding which behaviors the law should prohibit, as well as how to enforce these prohibitions, is debatable. I don't wish to weigh in here on the dispute between anarcho-capitalists and advocates of limited government. Reasonable people can and do disagree about just how far we can go in ridding ourselves of the state, although no reasonable person believes that society can exist without laws protecting each of us against coercive threats against our persons and property. But the state today does far more than enforce laws against murder, theft, and other obviously predatory acts.