If you take "Watch my baby" as "Watch my baby, but you can give him to your creepy step-daughter", you shouldn't be trusted with babies.
An analogy actually needs its parts to line up for it to be effective. She's not "in the passenger seat", she outright gave him the baby and walked away. If you want to extend the analogy to "Hopping out for a bit", then you have to imagine that the driver then managed to give the car to his crackhead brother in the twelve minutes I was away. If you wouldn't slap the driver for that, or call the cops, then would you lend me your car real quick?
Compare and contrast his reaction to his step-daughter with his reaction to a girl he knew, for a fact, was trying to entrap him, and possibly destroy his entire life:
He must have thought of the entrapment as little more than a harmless prank then, if that's how he reacted. Clearly his impression of the girl was one of a naughty little rascal.
So this is what negative IQ looks like...