Advice needed on "Hands part of the bat" myth

[TwoBits]

Long time umpire here going to coach my two sons' 10 and under rec team. The league uses FED rules with some modifications, and while the umpires are supposed to be certified, the ones they get for this age group are often teenagers or dads who think they know the rules even though they've never cracked open a rule book.

To my question: How do you explain to one of these umpires the falacy of the "hand part of the bat" myth? FED rules (as does OBR) does not state this clearly. As an umpire, I've tried to explain to coaches using rule 8.1.1d which states:
A batter becomes a runner with the right to attempt to score by advancing to first, second, third and home bases in the listed order when...a pitched ball hits his person or clothing provided he does not strike at the ball; or (1) If he makes no effort to avoid being hit, or if the umpire calls the pitched ball a strike......
I've also tried to use Casebook 8.1.1D: When may a batter be hit by a pitch and not be awarded first base? RULING: 1) The pitch is a strike. 2) The batter does not attempt to avoid being hit. 3) With no runners on base, the pitch is illegal and is not ball four. 4) The batter attempted to hit the pitch.

I've tried to show a coach that "hand part of the bat" is not listed as an exception, therefore the batter gets first base. Softball rules books are very clear on the subject, and this is one case I wish baseball rules books would follow.

Anyway, how do some of you other umpires handle coaches who insist on this, and some of you more knowledgeable coaches hand umpires who still believe this?