It's right there in Section 6 of the Hall of Fame's Committee on Baseball Veterans Rules, big as life:
(C) Those whose careers entailed involvement as both players and managers/executives/umpires will be considered for their overall contribution to the game of Baseball; however, the specific category in which such individuals shall be considered will be determined by the role in which they were most prominent.
Except the voters are not paying attention. Or maybe they're just confused, as the above codicil seems to say the voters should consider everything, except they shouldn't. So maybe some clarification is in order, along with the addition of "coaches" to the "managers/executives/umpires" list. Maybe then the voters would take Section 6, Part C with some seriousness. And when they do, maybe there will be a place in the Hall of Fame for Felipe Alou, with his 2,101 hits and his 15 seasons as a big-league manager. And maybe there will be a place for these other guys, too.
You know about Buck already: Negro Leagues player and manager, major league coach and scout, eternal ambassador and all-around Wonderful Person. When he wasn't one of the many, many figures associated with black baseball to be elected to the Hall of Fame a few months ago, the howls of protest could be heard from coast to coast, from The Sporting News to Sports Illustrated and every sports page in between.
The problem was that not quite enough voters could persuade themselves to establish a precedent. They were supposed to do what voters have always done and consider O'Neil as a player or a manager or an executive. Most of them bowed to sentiment, though, and supported O'Neil's candidacy (and the establishment of a new recedent). A few didn't, and O'Neil fell just a vote or two short of election. Everybody in that room voted his or her conscience, and I don't fault any of them for it. However, if the Hall of Fame ever explicitly supports the election of candidates based on "overall contribution to the game of Baseball," O'Neil obviously goes to the front of the line.