Monopoly of information is a monopoly.
When one person or enterprise is the only supplier of a commodity, in this case, information, then that enterp[rise or person is said to exercise a monopoly.
Inside information is an example. But it isn't the only one.
Trading regulations bar people from making use of inside information for good reason because it puts other traders and long term investors at a disadvantage.
Not only is inside information against the "rules" but is the monopoly of information.
According to Ackman's logic, monopolies are good because it helps so many. Please Bill, don't do us any favors.
We suppose the good comes from the profits the monopolist makes.
It's an interesting question with the possibility raising even more questions such as buy backs on bad news.
Disclosure: I have no positions in any stocks mentioned, and no plans to initiate any positions within the next 72 hours.