I don't know know about anyone else, but I thought this was the best episode of the series to date. Duke was faced with a horrible ethical choice, went against his own desires and convictions to do what he thought was best-- and may have destroyed himself in the process.
Yes, he was not thinking about what was best for him
, but what was best. While he's done that for people he's come to care about (Nathan and Audrey), we haven't really seen him do something for someone he barely knows, or really doesn't even know, because in the long run it was the best. He just couldn't see this boy being burdened by the same thing that cursed the boy's father, like he himself.
I don't think this has to destroy him, though it can.
Personally, i think he made the right call.