I don't know what material silencers are made from so if the silencer has some sort of coating such as chromium plate or its made from stainless / chromium steel then you wont have any problems since these are resistant to rust anyway.
However cleaning uncoated steel with kerosene will remove any wax or grease that was previously protecting the silencer which could indirectly lead to rust and then corrosion if its left for long enough.
Its not the kerosene that causes the rust its the fact that the wax and grease have been removed allowing water or damp air to come into contact with the steel. This causes the iron in the steel to oxidise / rust.
Kerosene could also damage any paintwork it comes into contact with if its not removed properly.