Different Interpretation
I thought the character of Sydney had some religious implications. Sort of like a human God. Up until Sydney whacks the hostage on the head, he's a completely selfless elder who loves but still holds his "children" accountable for their actions. Jimmy, SLJ's character, is more concerned with the gun he loves than with his friend John C. Reilly. I thought he was sort of a satan character (don't make me for a racist). Up until Syndney's past is revealed after Jimmy and Syndey talk in the car, my interpretation of the movie was these Sydney (good) and Jimmy (bad) fighting over the soul of John.
Once Sydney's past is revealed, things get a little bit grey, as they are in real life. Sydney's not all good. From the "this is not easy for me" speech Jimmy gives, he is rightfully calling out Sydney for his murder. He even calls sydney out on some of his bs self righteousness
So that was my interpretation. A clear depiction of good and evil, sort of a God vs. Satan thing, but played on a human stage and therefore is broken and not quite so clear. Estranged from his son, but likely because of his own faults.
if anyone chooses to comment, I'm going to ask you with all the heart and sincerity I have,we can hold back on an internet debate about "stupid christians" and "devil atheists." That is my hope.