Some fact checking.I'd say that's fair if you ignore the fact that the trilogy wasn't written by a single writer. It's glaringly obvious that it wasn't planned at all, which resulted in the clusterf*** that was ROS. TLJ undid too much of TFA for ROS to have a chance of being good; rather than being new and interesting, it reminded me of two kids playing with action figures in the sandbox.
"No, wait, it actually happens this way!"
"No, that's dumb, this is the way it should go!"
"Well, you're dumb!"
This scene in particular is one of the worst in the film and shows that Johnson plain didn't understand the character. I have a hard time reconciling this Luke with the Luke of the OT, and I think that's a pretty common opinion. Would Luke have had some PTSD from surviving the worst galactic war in recent memory? Of course. Would the guy who redeemed Space Hitler have decided to kill a child? Probably not, IMO.
First, Luke tried to kill his father before throwing away his lightsaber.
Second, Ben is in his mid 20s. Not a child.
Third. Luke in TLJ isn't Rian's doing. It's George's. He wanted Luke to be struggling with the dark side. In George's version something happens between Luke and his nephew. With the result being Luke's nephew being physically injured, and Luke going into self imposed exile.
Okay with that out of the way. Here's how I read that scene. Luke like his father is governed by his emotions. Chiefly, the fear of loss. Luke above all else fears to loose those he loves. So when Luke looks into his nephew's mind he's shown his greatest fear. The destruction of everything and everyone he loves. Fear takes Luke. That fear becomes anger. Which becomes hate. And Luke reaches for his lightsaber. Intent on ending it all before it can happen. Taking the quick and easy path. But then looks down. He can't kill his sister's son! But it's too late. Recall master Yoda's words to Anakin. "Careful you must be when sensing the future, Anakin. The fear of loss is a path to the dark side."