I'm not gonna get into the moralities of space exploration, but think of it this way. Jump back a few hundred years to before we had discovered all of the continents. Ridiculous amounts of money was spent in hundreds of failed expeditions whilst half of the populated world starved to death. They had no idea what was out there....they were looking for the edge of the world!! But what would we be like now if the monarchies of the time had turned around and said "nope...no more expeditions....they're far too expensive, we need to be feeding our peasants"...?
Now before ya all jump down my throat, I'm not saying that its exactly the same, but there are similarities. We have no idea whats out there. The discovery of a new mineral...or even gas...could be life changing for every single person on this planet. We shouldn't neglect the needy to do it, that would be highly wrong, but if someone wants to play around with military funds to produce this money then why the hell not. To me its all about balance.