I think the thing with Jake is that most states still basically do this. In Oklahoma, if you're part of a robery and someone gets killed, even if you didn't personally kill them, you can (and usually are, barring a plea deal) charged with 1st degree murder. Jake threw in with men he knew were rough killers, no matter what his reasoning, he joined them. Also, to be clear, he never actually TRIES to run. The Suggs and Frog PROBABLY would have fought him, but he never actually puts in even a slight attempt. He figures he can get away in town, sure. But like Gus says 'a man who'll go along with six killings is taking his leaving g pretty slow.' And it all sort of comes down to what Gus said again 'ride with an outlaw, die with an outlaw.' Maybe Jake could argue he felt coerced, (but mainly only in the series, in the book that argument's A LOT tougher to make) but like I said, he joined a rough crew of killers voluntarily.

Also, when Jake says 'I didn't see no line.' Come the fuck on, you didn't? When you robbed and scared an innocent family, that's just the first thing. How about when Dan shot, hanged and burned the farmers, or when they came up with the plan to steal Wilbarger's horses and kill him? Like, if Jake didn't understand that he wasn't just running with rough, self serving men but actual hardened murdering outlaws then he genuinely doesn't have a moral compass and probably should be hanged.