Sorry for the novel!
There's great arguments to be made both for space exploration as well as taking care of what we have now, and fixing the problems we have now. The problem is that if we always focus on the here and now then it is impossible to achieve technological/scientific advances at the current pace tat we do.
I really do believe more should be done to provide humanitarian aid around the world. My views on exactly what should be done are probably miles away from what everyone else thinks, but that's whole other debate. The problem is that most of the aid that developing nations recieve as donations from our government does not get to them. The level of governmental corruption and the power of the upper class in developing nations is close to unfathomable to most of us living in industrialized nations. Cash donations especially are mis-used. The best option, though it takes quite a bit of time, is to allow trade to continue as it does now and wait for companies to go searching for labor in underdeveloped nations. Ironically I had 3 midterm papers due just this week that all centered on outsourcing, and it is really quite a force to be reckoned with. It is allowing consumer nations (US, west europe, japan) to pass off the manufacturing work at dirt cheap costs to other countries, and provides us with much cheaper goods. While this sound like it takes advantage of poor workers, first consider the fact that most of these workers would be jobless without the existence of outsourcing. So far as I've found, this is the most effective way to inject money into underdeveloped nations, unless you start overthrowing governments and installing fair trade systems within th enew ones. Like I said before, that is a whole other debate.
My point is this- a very low percentage of the aid we send to developed nations actually gets to the people its meant for. Therefore, I think it is important for us to further our scientific research. Perhaps we will discover beter methods of growing food, or new drugs and medicines, or even new markets that could possibly emerge out of space exploration and ocean exploration.
The other big big reason i think exploration is critical is that the world's population is growing faster than our food production is growing. Currently we can make enough food for everyone in the world, and thousands still starve b/c we foreign aid is mis-managed. It won't be long before our poopulation starts over-whelming our food production. It could be as early as 50 years from now.
Unless we want our population to top out at around 12 billion, and then allow 3 billion people to slowly die off from starvation or disease, we have got to find new places to grow food, and new places for people to live. Scientists estimate that the Earth's population will stabilize around 9 billion people, because that's about how many resources this planet can provide.
There are a lot of issues facing the nations of the world, but now we are starting to see issues that may press us as a species. And I'm sorry, our world is in no shape to start dealing with problems like global overpopulation and global starvation or epidemics. This is why it's important to explore now. I'm sure that we won't find anything for a long time, but because of research and exploration we can learn how to build better rocketships, perhaps learn to engineer a better fuel/energy source. If we don't spend money on science then where will we get the technologies to achieve what we will need to achieve in the future?