Okay, first I'd like to make clear that I'm unambiguously for lower military spending.
But at the same time, I don't think it really matters. Firstly, the military is a large portion of the country's discretionary budget, but only a tiny percentage of the actual budget. That means that of the money Congress votes on, most goes to the military, but your taxes are spent on many things in addition. I forget the numbers but the military is around 5-10% of the actual budget I believe. If the military suddenly ceased to exist, taxes wouldn't really drop that much.
Secondly, the military IS going to spend that money. Government spending basically NEVER declines significantly. It's very hard to reduce spending in any given department, because by that time the generals and commanders have already made friends with your representative...
Thirdly, military spending impacts the economy at large quite a bit. I'd wager that the money made back in taxes from tens of thousands of military contractors, plus millions of college graduates from ROTC and military colleges, probably approaches the military's own budget.
If anything, I've been disappointed that a lot of this spending goes to massive new technology initiatives, rather than making military life a better option. There are millions of people in this country who don't have the social support - education, contacts, qualifications - to get a professional career, and I think joining the military would be an amazingly great option for them, seeing as they can still learn a trade before it's too late, see a bit of the world, and live in a strong community without the crime that might emperil them in everyday life. Consider the military welfare, except that Republicans support it. (Note: I realize that the military can't even fill it's ranks right now. Maybe if the pay was a bit better ... and a recession could speed things up too...)
But I'd really like to reinforce that while I support a large military, I don't support actually using it in wartime. I believe that soldiers on the ground can be a powerful diplomatic force, keeping peace and ensuring civility in many places where NGOs and the Peace Corps won't touch.
Of course, it's nice to have a bit of a military for minor wars, but let's face it, if there's any kind of instability in the PRC the US Army is toast. Last time America got on China's bad side twenty million people died. That's why diplomacy is vital in China.
Which leads me to another reason we should not even think about deploying missile defense. My personal guess is that one reason Powell & Assoc. are so strongly for missile defense is that they know how powerful our weapons are, but they don't know what other countries are going to be able to use them against us. So we could either annoy them by putting up a massive missile shield, which might work but if it doesn't millions will die, or we could actually try to engage countries around the world in active trade and cultural exchange, which might cost more (free trade will mean lost American jobs) but would pay off by ensuring that no one really wants to aim missiles over here, so we could ignore this wholee issue with the ICBMs and concentrate at home...
I could go on forever but it would be even less related to the subject at hand.