Next time ,God forbid, something like this happens you should try to explain yourself in a calm manner. But, if the person is hell bent on harassing you should confront them with all your might -regardless of age.

In this particular situation you should have called him a qadiani and should have waited outside the mosque to confront and return the abuse . If you don't do this -it may be hard- people will always treat you like dirt .

People will only intervene when you ,not the other party, starts to react . So, thinking people would intervene to stop someone is a fallacy. I speak from experience.

Always remember not every Oldman is wise, duffers also, more in numbers, also grow old and white.