hitting on arms during rebound

[RookieDude]

Here's a scenario for those of you who don't think it is a foul to hit a player's arm who has the ball in "your" verticality.

A1, who is 7 foot, is holding the ball directly above B1's head, who is 5 foot.
By rule, can B1 now jump up and hit A1's arm to try and knock the ball loose? (Remember, A1 is in B1's verticality cone)

You can quote rules all day long...but, common sense tells me this is a foul.