So, basically, we are posed here, 'What is the ethical/moral good choice?'...
If it was me, I would simply say, NO, I am not becoming involved in this materialistic barbarity.
The player has quite a lot of possibilities to choose here, if not a mere video game, and I myself, due to the game restraints, I am not really comfortable with any of them as existing in the game (meta-ethically as an Idealist-Kantian-deontoogist)... Not the only part of RDR I have "issues" with...
Once, on an abortive attempt to play the game "conventionally" (i.e. success = jungle-law, appropriation brutal and its semiotics of social tokens), I almost immediately thought - "How to avoid the law externally and completely, while still completing the side-mission, be the winner in every way?" - one word, guys: BAIT.
Oh my, the tragicomic drama of it all - THREE cougars almost instantaneously shredded to bits of flesh the poor screaming fellow, as I stood on top of a nearby rock - did the devs assign these rocks this specific geopoint, for this purpose? one wonders - felt guilty, that was the death-knell of my "conventional" go with the game, did not feel right inside... I can only imagine what modernly-conditioned amoral lemming conformist folk do in the game - serial killer's dreamland of perverted euphoria, I suppose - here is where the degraded vulgar quasi-nihilistic appeal connects RDR and the grossly low-grade pornography of the GTA series...
ANYWAY...
We are given "HONOR" for shamelessly robbing a pitiful old man whose life has been full of harassment by banditry... How is delivering the deed to the gold-idolator or keeping it one oneself, worse, in criminality, sinking tothe bottom of the possibilities - how does either, really, exist,as morally integral and tenable?
Only the nihilistic hellions of modernity, a vast global necropolis (see Rene Guenon), in their minds would consider merely and simply opting to not ravage, run roughshod over and/or murder an innocent person, as "honorific" or "honorable-meritorious", frankly... RDR in its worse elements is infected with the Nihilism of the epoch, in its best moments anti-nihilistic and inspiring - I can see how some vile trash like "GTA" might come from such confused mixed-up persons... Nothing is personal here: Socrates, Platon, Yeshua to modernly, Guenon, etc. all tried to warn us against the "beast" of Nihilistic materialism, to no purpose...
I wish RDR was more creative in moral imagination...
UNRELATED NOTE: Apparently I made a mistake earlier and am too lazy to go back and edit the specific talk page: my GUN-based kills in one dead eye session is 12 (possibly linked to the final dead-eye) - I did more with dynamite etc. but why even count that number as meaningful...?