Tyrannical government will drive freedom minded people to the stars the same way it drove people across an ocean...
This is why NASA is desperate to keep humanity earth-bound. Remember them fuming over the Dennis Tito flight?
when we leave we will take the technology with us
those left behind will quickly end up in the stone age
when we fly away we should not look back
perhaps someday we can return to see if things have improved
perhaps that is already happening