"OK!~ Your challenge is...to POLITELY try to persuade them
to change that opinion of theirs.
Are you up to the challenge?
What would you says to them? Where would you say it, to try and reach
them?"

I would then say we are living on one planet in the sea of a vast universe with more stars and "Earths" then there are grains of sands on all the beaches on Earth. Your future, the future of your children will not and should not be confined to living on one small but beautiful planet called Earth.
Space is the new frontier. You, the tax payer, are paying small part of your taxes so that NASA can help open this frontier.
Space development COULD contribute to our national economy to such an extent that would make the economic boom from computers/the internet seem utterly insignificant.