Advice needed on "Hands part of the bat" myth

[Kevin Finnerty]

I umpire and I coach.

As a coach, I had what should be a knowledgeable PONY umpire call a foul when a pitch hit my player on the back of the hand as he tried to lean away.

Umpire Tom: "Foul ball! Batter, back in the box."
Me (quietly and patiently): "Tom, the ball hit him, not the bat."
Tom: "Kevin, it hit his hand; the hands are part of the bat."
Me: [shakes head no]
Tom: "You're an umpire; I'm surprised you don't know that."
Me: [raised eyebrows, incredulous grin]

(Arguing in public with a guy like that in front of others is a sign of stupidity)