Avoiding Cognitive dissonance,is it a necessity? I want to know how strong is the pain of going through cognitive dissonance. Is it really so that changes in humans can be brought about by severity of cognitive dissonance struggle/pain ? Can I have a neurological perspective about it that might throw some light on the parts of the brain that are involved and the neurochemicals that might be playing a role in it ?
I think you're confusing science with politics.  The APA and other such professional organizations have not, to my knowledge, concluded that cognitive dissonance should be avoided or even minimized.  I'm unaware of any evidence that suggests that cognitive dissonance directly causes distress or suffering.

The position of psychology, as a science, is that cognitive dissonance is a phenomenon that exists and has certain properties.  There is no normative stance from the field as a whole.

What happens in these cases is that political groups engage in activism and argue that such things should be minimized; the same is true of stereotyping, for instance.  You may agree with the dominant political opinion, but it's not a scientific question, per se.