What would have been the reaction of the RSS had Gandhi been killed by a Muslim?

Same thing that happened in real life.

Nothing. Except that in this case, the massive anti-brahmin pogroms conducted by the Congressis in the wake of Gandhi's assassination would've been avoided.

Indians, mostly those of Hindu birth, have this weird disinclination to either understand or appreciate Institutional Power.

There's no way on Earth any bunch of what were and are essentially unarmed volunteers could go up against a massive mechanised colonial army and win, especially when the government of the day would be fully committed in ensuring that the would-be targets not only have the first right to India's resources and a third of India for their exclusive use, but free run over the rest of the land as well.

As it is, the entire story is tedious. So much ado over someone who was a tedious luddite nonentity at best.