There's no rule that says betting results in banishment from the HoF. That's just what the commissioner thought was just.
I say he should definitely be inducted. It's not like he was fixing the games. He was betting on his team, not against them. He's one of the greatest players in MLB history. Betting as a manager shouldn't have had nearly as serious consequences.
He was still breaking the rules, something that he knew was against the rules. He should expect and accept any punishment that is given to him by the commissioner.
No one's debating whether or not he broke the rules. He admitted to it himself. But just because the commissioner thinks that the ridiculous punishment of banning arguably the greatest hitter of all time from the HoF is justified, doesn't mean he's right.
It's against the rules to use steroids, but being caught using them usually carries no more than a short suspension. It takes four positive tests to actually be suspended for a season. If that's considered "fair" by the commissioner, then why does betting on your team, a very slight offense compared to 4 positive PED tests, carry a much larger punishment?