Also, Luke saw a vision of what Kylo was going to do. he foresaw Starkiller base, he foresaw everything that was going to happen.
"And for the briefest moment, I thought I could stop it. But it passed, and I was left with shame and consequence."
The exchange between Kylo/Ben and Luke is on par for Luke. Especially if it meant having to endure a Vader-archetype again. Imagine having to go through it all over again. NOPE.
