I based that statement on a project I read about in the 1970s called the WS-126A Bomber Defense Missile (BDM). It was intended for use on the B-1 but apparently was cancelled long ago. I can't find much information on it but seem to recall that it could fire backwards. I can't find any information on the Net to see if what I'm recalling is accurate or not.

Fighter pilots like to attack from the rear (check six!). A Stinger pointing backwards would be able to pick up the fighter pretty quickly with its IR seeker. A Predator is a pretty slow aircraft, cruising at something less than 140 MPH if memory serves. The altitude loss would probably be minimal. It might not be practical, but it'd surely get that fighter pilot's attention!

If the Stinger is facing forward, it wouldn't be able to lock on to the attacking fighter without turning into it. It'd have to know the fighter was in the area, say with some sort of black box to pick up the fighter's radar, or it'd have to be looking around constantly hoping to see the fighter before it was too late.

Don't rag on the Iraqi fighter pilots too much for having a hard time shooting down a Predator. The Predator is pretty small and probably has a fairly low radar and IR signature. In the Gulf War, there were at least a couple incidents were American fixed wing aircraft took out Iraqi helicopters. From what I remember, it was pretty tough in both cases. One was shot down by an A-10 using its cannon (that plane was dedicated at the Air Force Academy last week) and the other taken out by a laser guided bomb (!) dropped by an F-15E.