Well, if you had 1,000 Barretts lined up, SOMEBODY would have to hit it, right? But then I guess the terrorists, lacking 1,000 men, would say "Let's just call Muhammed and have him send us a machine gun and bring it in from Mexico on the back of illegals". Then Abdul would say "Muhammed, you silly man, for that kind of money we can get a shoulder SAM from Saddam!" Then Muhammed would have to tell Abdul the bad news about Saddam.
Nope! Not a chance. Even if all the rifles were scoped. The dynamics of target velocity, altitude, winds aloft, projectile velocity, projectile profile, etc, all conspire to miss the target. I could go on but even a thousand rifles do not raise the odds of a hit up to 1:1. It is obvious that these "critics" have never hunted desert dove or Canadian Geese on the wing with a 12ga., or they would know the impossibility of hitting an aircraft either close and fast or high and slow.
What I find to be curious about these critics is that they also tend to be against the US having an Anti-Ballistic Missile system based on the issues of "accuracy" and cost.