The reason why the book should not be published is because it contains false information that defames the reputation of the New Kadampa Tradition, such as the NKT is in league with the PRC. Where does freedom of speech end and being able to publish defamatory lies begin? This is the reason why the libel laws exist.
The book also appeared to be repeating the false claims published by Dreyfus and others about Dorje Shugden and the history of the practice, thus further 'demonising' this Deity and assisting the Dalai Lama in accomplishing his agenda of destroying the practice.
It's also clear from the title headings that it was not neutral -for example, The Arrogation of Manjushri Institute: While the Cat’s Away
In case you're not sure (and I wasn't), 'arrogation' means 'To take or claim for oneself without right'. The implication is that Geshe Kelsang stole Manjushri Institute from Lama Yeshe which is completely false. There was a vote of the Residents who all wanted Geshe Kelsang to stay and be their Resident Teacher. It also became clear that the FPMT managers were going to sell Manjushri Institute to fund other activities, something the community did not want, so to protect the centre and community they eventually split from the FPMT. I doubt very much from the title of this chapter that such information (including the fact that the FMPT were raising money through drug smuggling) would be mentioned. This is what really happened:http://www.newkadampatruth.org/smear-geshe-kelsang-gyatso-stole-manjushri-institute-from-the-fpmt
This being the case, why should NKT allow lies about the 'arrogation' of Manjushri Institute be spread about? Allowing lies to be spread in the name of 'free speech' is not helpful. Anyone can say, for example, 'Dorje Shugden is a demon' or 'NKT is in league with the Chinese Government against the Dalai Lama'. They are free to say this, but since it's a wrong view, it's not helpful to spread it around. The various accusations made against Dorje Shugden, NKT and the WSS by people who are misinformed or even malicious, as Middleway said, affects people's faith and therefore interferes with people's spiritual lives. We can therefore say that books containing these false claims are maras and every effort should be made to prevent such obstacles from arising.