"I tend to think putting basiji snipers on rooftops to shoot kids down in the street means the Iranian government is not especially concerned about public relations at this time."
I think they are exactly concerned with public relations. Shooting citizens, but not openly on TV means the news spreads by word of mouth. It will spread and it will bring fear. But you can't prosecute based on word of mouth, plus it has the element of exaggeration. The other countries are afraid to do anything, and soon the local Iranians will be to afraid to protest as well.