This guy lives in a fantasy world where every single thing the government does is decided by brain geniuses looking at cost-benefit models. The much more simple explanation that the government either wanted to shoot it down but couldn't until it drifted lower, or that the response wasn't coherent at all with some people wanting to shoot and others preventing them.

Maybe it was intentionally left alone because of the propaganda value, but honestly even giving them that much credit is a stretch IMO.