I've always found that human extinction argument rather dubious. The main mechanisms of extinction in those cases are atmospheric dust and fallout. If we can maintain a closed ecosystem on Mars, we can do it underground, for a fraction of the cost, much less danger, and with a crew that rotates.

Dinosaurs died out because they didn't have nuclear power plants or indoor greenhouses.

A major impact would still be a tragedy of unimaginable proportions... but putting a bunch of technocrats on mars isn't going to change that either.