Getting back to topic: Forget the moon.
How about the complete loss of manned spaceflight capability? He's proposing cutting the entire constellation program, which is the Ares lift vehicles (all of them) AND the Orion space capsule.
Shuttle can't last and really needs retirement. Endeavour, the youngest, is 19 years old now. There are only three left and given the stresses they've been exposed to I'm surprised we haven't lost another one already. There is nothing else except the Soyuz, which isn't that swift of a vehicle and has it's own funding problems. You'd be completely dependent upon a foreign semi-hostile politic for your access for at least 8-10 years, which is a VERY long time in global politics.
The overlying assumption in all of this is we can always build one later.
Really?
Think you'll have the engineers to do it then?
Average age of the Aerospace Workforce = 54 (source)
http://www.britannica.com/bps/addit.../Americas-Aerospace-Workforce-at-a-Crossroads
Very few future Aerospace Engineers in the pipeline now. Can you blame them? Why would America's brightest want to enter this field with this kind of political environment? Kill the F-22! Kill Constellation!
I know! Let's let Private Industy build it! We can have a Space Taxi!
Yeah, well, Rutan's group (and others) have made progress, but there is a vast difference between achieving 60 miles altitude and being orbital. Sustained Orbit is beyond even that. Private space taxi may get you up where things turn black, but sustaining orbit requires significantly more engineering than they have the assets to provide.
If the Powers That Be want to kill the Moon/Mars missions, fine. But don't hamstring the only viable option we have for continuing manned spaceflight too. And give the bright 18-22 yr-old wanna'be engineers something to dream about working on.
Don't throw the baby out with the bathwater.