All game show winnings $600 and over are considered income and are subject to state and federal taxes. Bull might be able to deduct his donation to the boy's club for the $7000 he gives, but might still be on the hook for what's left of his winnings, leaving Fielding without the ability to get his cut (or at least as much of it as he was anticipating).
While trying to convince him to go on the show, the game show host calls Bull "Mr. Shannon" even though they had not been introduced.