I'm sure there is a 'rational' [='sensible, reasonable'] explanation for his decision.
Humans are 'rational' beings. [=are able to use reason when thinking about something]
No 'rational' [='sane'] person would behave like that.
(..) if you're gonna start more shit around my baby girl. You can relax for now. I'm not gonna murder you in front of your child, okay? That's being more rational than Bill led me to believe you were capable of. It's mercy, compassion, and forgiveness I lack. Not rationality. (..)2003 Kill Bill: Vol. 1