Gaal the son of Ebed came with his brothers, and went over to Shechem; and the men of Shechem put their trust in him.
Gaal's appeal to the Shechemites was quite logical.  Hamor was a powerful figure in Shechem when Jacob bought that piece of ground from him, but whether or not he was the "father of Shechem," as alleged by Gaal is not known.  The rabble-rouser's argument was, "Why should we serve these Jews?  They were once inferior to the great founders of our city!"