(an instance of) defecting , e.g. to another political party (or its leader), to another religion etc

abandonment

(an instance of) denying; refusing a request

dismissal, refusal of belief in

the state of not believing

doubt, scepticism

(a feeling of) uncertainty

lack of faith, conviction; questioning

a person or thing that is not included

leaving out

a feeling of sickness or disgust

sickness in stomach; revulsion

(an act of) denying, refusing

contradiction, denial

to give too much time or attention (to something); complain about unimportant details; to annoy (a person)

nit-pick

(hidden) corner; secluded

corner, cubbyhole

a statement or feeling of dislike, disapproval or opposition

argument, disagreement

a serious or formal declaration

objection

an unkind refusal (of an offer of or request for help, friendship etc)

turning away; ignoring

(an instance of) an act of refusing

denial of responsibility; unwillingness