So when someone hits you and try to hit again then based on your arguments you can hit them back on self defense as you are preventing them from attacking you. Without someone attacking you first you don’t even know whether they have the intent to do it. This is what the other advocate is also saying.
Moreover, as an advocate, I don’t think our indian courts take slapping each other so seriously to warrant a criminal procedure for 10-15 years. This is over exaggerated.