I'm still confused about the bear. How is a human not existing a danger to others? A human not existing is really only dangerous to the human race once it reaches some critical mass that will essentially prevent any new humans from existing. I don't see how this is at all analogous to unleashing a bear in a populated street. Each instance is inherently not dangerous by itself. You can't say that for the bear.
By that reasoning, why should we do anything to reduce green house gas production or any kind of pollution? We'll figure out how to remove it from the environment or make it otherwise non-harmful eventually. May as well go full steam ahead now in that case, right?
I also highly contest the notion that preventing a human from coming into existence is anything like removing an existing one. If you were forced to chose between killing somebody or destroying a viable embryo scheduled for implantation, would you seriously have all that much trouble deciding?
>I'm also rather uncertain how your 'caged bear button' example is relevant here. The only dangerous bear I can see in this context is the overuse of resources. In which case the example seems to be advocating that the best course of action is to expose people to the danger by default, unless people take constant action to keep the danger contained. I'm not sure how this argument is supposed to attack the "keep populations controlled" line of thought.
The dangerous bear in this case is our reproductive capabilities declining. A human that is prevented from coming into existence when it would normally be able to is the same as removing an existing one.
We will solve it, we just need to start and provide incentives for it.