If you get up close to the door, they clip thru it to the point where you can damage them. Hey, it's not cheating!
I'm actually all for tactics like that when all else fails, but I have to believe the designers had some notion of how to best make it past this particular level and I still haven't heard from anyone in the year since its release who's strategy has been anyting more than "run like hell and get lucky". Maybe I just missed something . . .
Is that the one where you can move a chair down to the door and keep it open while you pick off all the guys that come up to it?
That's a different area, but a very good trick if you get tired of reloading.