The fear that we will accidentally destroy the planet seems remote. Merely economic incentives lead us towards designs that are simple, inflexible, and highly efficient in a very specialized environment. I do not expect that everyone will immediately agree with this assessment. The point is not to resolve this issue today, but that we, as a society, need a mechanism for resolving this and other complex issues. We can hardly decide on a wise course of action when there are still fundamental disagreements about the basic nature of the technology whose development we are trying to guide.
Accidents are only one cause for concern.
A greater cause for concern is deliberate abuse. New technologies are used to make new weapons. This is a complex question which I and others have considered for decades. To the best of my knowledge, there is as yet no clear answer. From a practical point of view, the answer to this question matters a great deal.