I don't believe that there is an argument for why A&M, LSU, or SC don't deserve a BCS bid other than there's only so many to go around and the SEC already had 2 spots. Besides, that's a separate argument, imo, since NIU took Oklahoma's spot.
My argument for why NIU deserves it's chance is right now. It's 17-10, NIU just recovered an onside kick and is moving. It's exciting. The best thing about the NCAA bball tourney is the first 2 rounds and the last 2 rounds. We all love the upsets and close calls and we love the big boy slug fests in the Final Four. The BCS has some of big time games in Bama-ND & KSate-Oregon. I'm enjoying watching these kids from NIU hang with a one time contender for the BCS title game. It's good for college football if it isn't great for the bottom line.
Edit: NIU just turned it over and got nothing out of their drive but they're still within 7 late in the 3rd. Hardly the slaughter that it should be if NIU was really so undeserving, imo.