User blog comment:JackMarstonDiabloJr/Who hates the end of RDR/@comment-1265875-20110907225134

And to address your "duty" comment.

Marston was forced to comply with Ross 'orders' because they'd kidnapped his family and were threatening to do them harm if Marston did not cooperate.

This falls quite short of the definition of "duty" and closer to that of "coercion".