There is an old Gypsy saying: "I against my brother. My brother and I against our uncle. My uncle and I against the outsider." As Jack himself has said, everyone is free to say and so as they will, and their reps will reflect it, but no one may betray each other. Clockwork crossed that line. Honor among thieves is more than a moral imperative: it's a necessity of business. If your Johnson is always going to try killing you, you'll stop taking jobs. If the fixer always rips you off, you'll stop buying from him. And if your team is always trying to tear itself apart, people end up dead. Professionalism involves a degree of loyalty, and you're only as good as your word.
Unless you're Kane, in which case it's more killer luck, talent, and a really big ego.
Which brings me to my next point: a fair number of folks on JP are hardly whitehats. Hannibelle could hardly be considered entirely trustworthy, Johnny No has stated firmly that he will do almost any job if the money is right, Puck may be trying to make right, but he's got a whole lot of bad still weighing on him, and Rigger X has a bad habit of killing the teams he works with. There are more beyond, but I end to see the activity on JP as less about "doing what's right" and more about camaraderie. That and the fact that most of the things that they unite to fight against are the things which are utterly reprehensible or are commonly considered evil, even to criminals. Consider that child molesters rarely last in jail. Same for people who kill children. You may steal, you may lie, you may even kill, but you're not out there kidnapping babies. That kind of activity reflects poorly on the rest of the community, and pushes at the thin border that separates most shadowrunners from being utterly psychotic mad dogs. Runner like that, you'll note, tend to get put down.
And for lack of any better explanation, Clockwork made the mistake of peeing into the well from which he drinks: he went after people in his own network, people who have become friends, associates, contacts. And any savvy runner knows you take care of the things that take care of you, whether it's your gun, your body, your chrome, your wheels, or the VPN you subscribe to that gives you all that sweet intel and all those job leads.
It was a dumb move. Underdog he may be, but sometimes, the outsider really DOES deserve to be there.