>>123613676It's a fairly standard cape book plot, it's not about protecting Selene as much as it's about Logan trying to stop Rachel crossing the line and becoming a killer, because by cape book logic, once you kill one bad guy who had it coming, you'll default to lethal force every time, and never stop, you'll become as bad as the villains you fight. He's willing to fight and injure her to save her from this.
Where the story falls down is that it makes it clear Logan doesn't hold himself to the same standards, but he doesn't just kill Selene himself, because somebody needed to.