i am of the opinion that the word "mochi" was used by the lyricist to represent a profession,and not a perticular caste. Even our kindergarten books refer to a cobbler as mochi, and a goldsmith as "sunar". A person who deals in "sona" is a "sunar". If you will not call a person working in a bank a banker, then what would you call him? Why create this unnecessary fuss just to gain some political mileage. Our so called politicians would be better off utilising their energies on something constructive like improving the lives of people who they say have been represented in the song.
