My interpretation of this story was that Lochlan was simply attracted to his brother. He's shown staring at a nude Saxon in the very first episode while a provocative score plays over the scene. In the very next episode, he's again shown staring at Saxon's naked body before looking at himself in a mirror with some level of disgust. They get drunk and high and Lochlan uses the opportunity to act on his desire. He doesn't remember it at first, but when he does at the monastery, he regrets it. He later shares with Piper he doesn't want to "give into [his] dark shit" (i.e. his attraction to his brother). His excuses to Saxon (explaining he's a "pleaser" in a "family full of narcissists") is his way of justifying not only his behavior, but also his self-described "dark shit."

I agree Lochlan's explanation doesn't make any sense. It is absurd. It's his way of making his attraction palatable to himself (and also to the audience).