My Google search using the terms:

Warragul aboriginal massacre   

turned up this site.


      Museum Victoria: Fighting Hills Massacre, 1840

http://www.museum.vic.gov.au/ed-online/encounters/Journeys/Robinson/Fighting_Hills.htm

And the bibliography lists this book which was published in Warragul, but the massacre happened at Fighting Hill(s) in 1840.

Gardner, P.D., 1983, Gippland Massacres... the destruction of the Kurnai Tribe 1800-1900, West Gippsland Community Education Centre, Warragul, Vic.

Having recently travelled in Victoria I wasn't sure if we had passed through that area, and that might be why it rang some bells for me, or whether I saw something somewhere else.

Not knowing the area in question, I wondered

a) whether the Fighting Hill(s) area is near a place or creek called Warragul Creek
b) the songwriter changed the name to Warragul, and the surname of the Whyte brothers to McMillan and the boys.
c) it has nothing to do with that massacre
d) none of the above (grin)

Helen