I know this isn't the popular answer, but I think space exploration is a huge waste of resources. I mean, we can spend kajillions of dollars to find out that there is an Earth-like planet several billion light years away, but really, what good does it do us to know that? I mean, does the human race become any greater for that knowledge?
I don't think so.
Space is not in danger from mankind; it will always be there. The wonders down here on Earth are not, and with our finite resources it is them that we should pursue. You want exploration? We've got the vast depths of the ocean to work on. We've got rainforests full of plants and animals not yet known to man. Perhaps in some distant future, when we reach that utopia state where there's peace and prosperity and good will toward all, we can turn to our governments and say, "So, about the stars..."
I just don't see space exploration as something tax dollars should be going toward, not when our country is mired in mountains of debt already. If space is so wonderful and profitable for mankind, private enterprise should be allowed to pursue it to their heart's content. (Although given how business interest has mucked up other aspects of the environment, I'm glad they haven't yet.) Let government money go to causes a little more down to earth.