Deadly accurate flak tore through the bombers. More often than not friendly bombs dropped from above.
My father worked on these statistics. He said that it was obvious that the smallest risk came from bombs from aircraft above you. The bombs were supposed to detonate at ground level. If you hit a plane on the way down, they should not explode. The antiaircraft fire on the way up was intended to explode when it got to the right height. The best thing you could do was to send in three levels of bombers at different heights, and swamp the ack-ack crews with too many things to shoot at. The anti-aircraft fire fuses could only be set to detonate at one height. There were proximity fuses, but they probably did not work very well.
So, given three bombing levels, which one should be the safest? Actually, the bottom one was the safest. You might have a dead-on hit with a bomb from the two levels above; but you were lower, which mean that any anti-aircraft gun had to track faster in order to follow you.
I guess what he could have done was to set up scale models in an aircraft hanger, and show the pilots how hard it was to hit an aircraft below, by dropping peas or something. But I doubt if anyone would have understood. Somehow, bombing your own chappies was much worse than taking one from Fritz. Go figure.