In this novel, as well as in real life, the tendency is that if you fear something you destroy it.
However these fears were derived, and whatever the reason behind it, the effect of them is the same.
In Waknuk, deviations are feared to be the devil's mockery of the true image. One also should have trepidation towards them because of competitiveness issues. A man with an extra arm could handle more tasks simultaneously. This makes the man or woman of such an ability somewhat superior when compared to others that don't possess it. In the novel this fear manifests itself into a need for the Waknukians to sterilize blasphemies, and send them to the Fringes.
The Waknuk society also fears those who would question their ethics. If they were proven to be right then the customary Waknuk belief system would be found to be wrong. This gives anybody, and everybody the feeling of stupidity.
This sensation, as you can well imagine is not a desired one. Because of this fear any one who criticizes their beliefs is swiftly brought to justice. The courts will likely rule that the prosecuted had some kind of affiliation with mutants, to develop such an attitude. He/she will be thought of as a threat to society, and killed, or sterilized before being sent to the Fringes.
The same people also developed a great dread towards David, and the other thought-thinkers he associated with. They were afraid because they remained "at large" for quite a while, before becoming discovered. These deviants could also communicate without speaking. This quality made them seem as somewhat superior. If they could do such a thing, then surely they could cooperate together more efficiently. The Waknukians also were unaware of just how many of these telepaths there were. Because of all these factors the people of Waknuk wanted all of the telepaths captured, and brought to bear against their deviations. Michael states, "They are scared of us. Ready to break us down in the attempt to find out more about us - once they can catch us.
You mustn't let them get hold of Rosalind or Petra - far better to kill them yourself than let that happen to them." (1995 page 143) This clearly illustrates that the people of Waknuk fear them, and are ready to destroy them for that.
The Fringes People aren't necessarily any better. Upon meeting David, and inquiring about why he was in the Fringes, Gordan states "It's you they're after, and you've brought trouble this way with you. Why should we care what happens to you? Quite easy to put one of you where they'd find you" (1995 Page 162). He fears the outcome of the Waknukians retrieval of David, Rosalind, or Petra, and would normally of killed them if he himself, hadn't died first. The Fringes people also feared the civilized parts to the northeast. This fear arised from their abandonment by these very people, and persecution from them. The Fringes People use this fear to destroy any of their neighbors they get the opportunity to do so to.
The people of New Zealand, however, needn't be scared of anyone. Their technology is far superior to that of everyone else's, and they have the ability to think together. The Sealand woman does state that, "we have to preserve our species against others that wish to destroy it - or else fail in our trust." (1995 Page 195) This means that that which we fear must be destroyed for reason of self-preservation. She also states that, "They are alert, corporately aware of danger to their species. They can see quite well that if it is to survive they have not only to preserve it from deterioration, but they must protect it from the even more serious threat of the superior variant." (1995 Page 196) She's referring to the issue that if we fear something, we must protect ourselves from it, by attempting to destroy it.
In real life this very idealism has been the cause of many a horrific event. You could say that the Germans feared the effect the Jewish people would have on their civilization, so they set off to destroy them. After the bombing of Pearl Harbour the Americans learnt to fear the military might of the Japanese. This led to the attempted destruction of their war machine.
Animals have also felt the blow of this idealism. In North America timber wolves were hunted because they were feared by farmers, and indeed most people. This was partially responsible for the wolves decimation of both range, and numbers in North America. When grizzly bears become to habituated to people in Banff they are feared to be on the verge of attacking people. Because of this the animals are commonly put down.
From the bears in the mountains to the Columbine High School incident, the fact is that that what one fears one destroys is consistently brought before us. In this high school the murderers were afraid of the taunting by fellow classmates, and bullying so they went on a rampage of none other than destruction.
The Cambodia killing fields was another atrocity to grip our world. In that country the Khmer Rouge feared the highly educated members of the country. They believed that these people would influence others that their policies would lead to a deterioration of Cambodia. The Khmer Rouge decided that it was essential to murder all those people, for that very reason.
The world around us, and indeed the world in Chrysalids as well, is constantly encountered with the idea that what one fears one destroys. This is evident is everything from animals to government, and seemingly consumes everything. The simple answer to why such a thing occurs so often in our lives, is self-preservation. We fear something because of the negative effects it might wrought upon us, so we destroy it so the threat disappears.