Rajmohan Gandhi told the BBC his grandfather would also have tried to organise "something dramatic" - perhaps a mass fast - to show how unhappy most Muslims were that their religion was being linked to terrorism.
Asked what he would have made of al-Qaeda leader Osama bin Laden and the Islamist Taliban militia in Afghanistan, Rajmohan said: "He would have stood up to them."
"The Muslim and non-Muslim issue was a very important issue in his life in India, and he was killed because many Hindus thought he was friendlier to the Muslims than was necessary," the former Indian parliamentarian said.
"So today, he would never agree with the idea that there's something connected between Islam and violence or Islam and terrorism. He would totally oppose that idea."
Rajmohan added that his grandfather "might have recommended to the Muslims of the world who were unhappy being hijacked by the terrorists to say how about demonstrating your dissociation with violence through a fast if need be".
One wonders whether moderate Muslims could have been shamed by the Mahatma into such a grand demonstration, or whether he would even have lived long enough to carry out the effort. It's fairly certain that the Islamofascists would have had no qualms about murdering him.