There's often a "we should fix problems on earth before looking to space" theme. We can be as equal, progressive and fair as we like and an asteroid still wouldn't give a damn and wipe us out anyway. Should we survive asteroid attacks, the sun will expand and burn the planet dry anyway.
We have to do both. Defence of the Earth (dramatic phrase, but see subject above...) has to be studied, funded and run. Along side that a long, probably multigenerationally long, programme of "how do we survive when the Earth is uninhabitable" including the ability to leave Earth and live elsewhere. These programmes are fundamental to long term survival of the human race.
I think one of the problems is that it all sounds very dramatic, big and sci-fi. But it isn't - we have direct evidence that the risk already materialised once and wiped out most life. We also have evidence of the expansion of the sun. All these things are certain, so we have to look at them as reality and not fiction.