The idea that Zuckerberg now voluntarily wants to sacrifice some of his own power and money for humanitarian purposes is, at best, highly doubtful.
Whenever the head of a company calls for more regulation, invariably it is to serve their own interests. While Facebook is not really a monopoly now, with sufficient government regulation it will be. Unnecessary regulation creates barriers to entry that smaller companies will have difficulty overcoming. Eliminating competition and protecting himself and his company's exposure to liability are likely Zuckerberg's motives here. If you think he is being altruistic then you are fooling yourself.
Fortunately, decentralized solutions will always stand in the way of any potential true monopoly.