It is the right of a person to have autonomy of self, regardless. Full stop.
It is your responsibility to understand the consequences of your actions to the best of your ability. Because it's you who has to live with it.
This doesn't mean that I have to agree with your behavior, it's also not my responsibility to stop you from doing something to yourself. However, I will warn you about consequences if I can. It's the best I can do.
So yes, let the adults do what they want.