"We Didn't Start The Fire" is about as genuine a folk song/political song as "Eve Of Destruction". In fact it is down there with the dregs of what Diane ís referring to as "commodities". I personally dislike it more than "Sugar Sugar" - which happens to give me toothache, because at least the Archies were not guilty of the fundamenal dishonesty of Barry McGuire and Billy Joel.
In fact folk song is exactly as McGrath says - sometimes political and sometimes not. That goes for any art form.