The tarnish on silver and copper is a form of oxidation (so is rust), but it forms a patina on the surface and does not actually destroy the metal in the same that rust will cause iron and low-carbon steel to decay and eventually crumble. Any good silver cleaner/polish will do a good job of cleaning your silver banana plugs, although you should be careful to remove all of the cleaning agent (Q-tips are helpful here).
Best way of removing rust from silver or other
I have a pair of Audioquest cables with silver banana plugs that have tarnished due to humidity and time. I wonder which is the best way of removing this tarning without damaging the plugs permanently....Btw, is this sort of tarnishing detrimental to sound or just something that is not aesthetically pleasant?