In Star Wars: The Last Jedi there is one scene between Rey & Kylo Ren when they are force-linked, where Rey calls Ren a "murderous snake" and a "monster".
Although Kylo begins to point out what he perceives as Rey's ignorance of past events, he does not deny what she stated and replies, "I am a monster."
Now perhaps this was just a disarming tactic, but are there any other reasons with some sufficiant evidence to prove what Kylo Ren's motivations were here in not fighting Rey on her characterization of him?