If you want to know better about immigration laws, you should have asked your children to drop their US Passports in Mumbai and try to enter US. I am sure, they would have failed to enter.
IMHO, the officials honestly deserve every rupee of their salary for that day BECAUSE for a change, they did their job sincerely. Forgetting visa documents is an unpardonable mistake and the officials are supposed to follow rules whatever it may be, they can not be letting their hearts dictate what they should be doing in their jobs. If officials start going by their heart, there would be no law and order. If teachers start going by their heart, you would see 100% literacy floating everywhere with people not knowing basic alphabets. Learn to appreciate officers who do their job sincerely, because it is a rare scene especially in the developing countries. I am with you on the pain of going through such a great inconvenience BUT at the same time can't agree with your point that the officers were inhumane. I am sure, you yourself would have lost even more pride of being an Indian had your children, who are not Indians, been allowed to enter India without Visa.
