Brian,
Don't be too hard on your politicians. Well, maybe in general it is warranted, but maybe not for this decision. The way I look at it is that oil is undoubtedly going to continue to skyrocket in price in the future. Ten years from now, if the Hubbert's people are correct, there could be a 20%+ shortfall in global supply for oil vs. demand. If that's the case, oil could easily shoot to $500/barrel or much, much more.
At that time, US politicians can reverse their decision and allow drilling. And in the meantime, they'll have saved the US-accessible resources and bought foreign oil while it was "cheap." Oil from the Middle East may not seem that cheap today, but five to ten years from now, we may be looking back in hindsight and think, "I can't believe the Saudis let us buy all of their oil for under $300 per barrel."
Stranger things have happened.