Should we colonize space to mitigate existential risk?

Sounds good in theory, but we don't have the expertise to do that. If we did, trips to Mars wouldn't be classified as 'one-way suicide' certainties. The only way people can survive in space or on Mars is if there is the whole of Earth's backing behind them. No Earth, No Survival.

Actually, one would be fine with just Elon backing them.

"Everyone agrees that we should try to avoid extinction"

Perhaps I'm an outlier here but I don't see why we should do anything in particular to ensure the survival of humanity.

You're only an outlier because of how rare logic is today ...

I think we should get our own house in order before wasting money on, literally, pie in the sky.

We're on our way to polluting every square inch of the only known habitable planet, and already causing mass extinction.

Thus how can anybody prioritize sending a few people to Mars?

no. we should use our knowledge to harden our planet against our kind so that we can have security and longevity to develop real space faring tech

Yes.