It is certainly the case that this dystopian novel contains much cruelty and that there appear to be far more incidents of cruelty in it than there are of kindness. Sometimes it appears that cruelty and kindness go together, as the dog-eat-dog mentality of this world dictates that you have to be cruel to be kind. An example of this is when Uncle Axel kills Alan in order to protect David and the other telepaths. Uncle Axel has to be cruel in order to be kind, because if he had not killed Alan, he would have revealed the secret of the telepaths with terrible consequences.
In the same way, cruelty is carried out even by those who are apparently "good." Rosalind has to kill in order to ensure the survival of herself, David and Petra, and finally the woman from Sealand is perfectly happy to kill all of the men from Waknuk and the Fringes in order to rescue Petra. Note how she explains how the threads that fall from the helicopter work:
They're all dead. The plastic threads contract as they dry. A man who struggles and entangles himself soon becomes unconscious. It is more merciful than your arrows and spears.
David reports that there was no "callousness" in the woman's mind as she says this, and she treats this act of cruelty, which in her mind is "more merciful," as being necessary in order for her to secure her goal. What appears to be an act of kindness actually seems to be based on much cruelty in the form of the deaths of lots of men and animals. The novel therefore definitely presents a world where there is far more cruelty than there ever is kindess, and where even "good" characters have to engage in cruel acts in order to survive.