Sure downvote reality, that will make it go away. The sort of points I want to see, the bankruptcy of "I have no plan".
I'm downvoting you because you're wasting everyone's time and being demotivational about a great thing. The only true progress is technological.
I don't know if it's a realistic problem, my guess is it probably is, but not significantly worse than what we already have with nuclear proliferation.
The basic problem is pretty real, though: we're at a stage of technical development where it's really easy to render the planet uninhabitable, while we're at an uninspiring level of cultural development that makes it really hard to produce sensible policy.
However, I tend to agree and say that it would be hopeless to try consider something with a bazillion influential moving parts and as volatile like human civilization something we could try to "make safe" before working on better space access, which itself might well increase our robustness.