Dammit! I was thinking of this one.
If I’m not allowed to hit problem customers, then the terrorists have already won.
If I’m not allowed to smack anyone who uses the tagline “then the terrorists have already won” *then the terrorists have already won.
If nude photo’s of our lady dopers are not sent to me, then the terrorists have already won.
If you do not take me seriously on this request, then the terrorists have already won.
[sub]If Trinity lets me live through the night for making such a request, then the terrorists have already won.[/sub] 
If the terrorists receive their Publisher’s Sweepstakes entry, then the terrorists may have already won!
If you don’t stop this bus right now so I can get off and find someplace to take a HUGE CRAP, the terrorists have already won!
If you don’t have a room for the night in a nice comfy cave, the terrorists have all ready, one. (Call in advance of arrival, American Express NOT accepted, but will take goat’s milk in trade.)
If you don’t talk to your kids about drugs, the terrorists will.
If you don’t stay on the line while an operator redirects your call, the terrorists will have already won.