I could present facts, data, essays, to try argue both sides of this, but I won't. That is way too much effort. I will argue only the merits of what it has done for mankind, like inventions, technologies, cinema, television, and why it will save us.
There have been some really great discoveries and inventions from space exploration. The water filter. Safety grooving (also known as the rumble strips on the side of the roads). Cordless tools. Anti-corrosion spray. The redemption of Bruce Willis' career. Who knew rough necks could save the world from a giant comet! There are plenty of others, you get the point. Speaking of movies, how about all those great space movies?! Apollo 13. Gravity. 2001: Space Odyssey. Wall-E. October Skies. That one with the weird looking guy who sings about holding the world in his hands.... there was a chimp in it. I can't remember the name of the film.
We have space exploration to thank for many of our heroes. Galileo laid the foundation for guys like Stephen Hawking and Albert Einstein, who said that, "he bears more of the responsibility for the birth of modern science than anybody else" and that "the father of modern science." Children grew up and wanted to be Neil Armstrong and Buzz Aldrin. Those guys set the stage for guys like Gru, who became a wonderful father and terrible super villain.
Where the hell are we going to put all of the trash and rich people when we are about to go extinct!? That is real kicker. The world will spiral into chaos after a nuclear warfare, pollution, or a zombie apocalypse and what will we do? The government will be broken. People will be lost. But the Space gives way for a rebirth. Look at Transformers.... okay. I am totally kidding.