dissenter n.

mid-15c., dissenten, "express a different or contrary opinion or feeling, withhold approval or consent," from Old French dissentir (15c.) and directly from Latin dissentire "differ in sentiments, disagree, be at odds, contradict, quarrel," from dis- "differently" (see dis-) + sentire "to feel, think" (see sense (n.)). Ecclesiastical sense of "refuse to be bound by the doctrines or rules of an established church" is from 1550s. Related: Dissented; dissenting.

The noun is 1580s, "difference of opinion with regard to religious doctrine or worship," from the verb. From 1650s as "the act of dissenting, refusal to be bound by what is contrary to one's own judgment" (the opposite of consent). From 1660s as "a declaration of disagreement." By 1772 in the specific sense of "refusal to conform to an established church." 

Has there ever been a society which has died of dissent? Several have died of conformity in our lifetime. [Jacob Bronowski "Science and Human Values," 1956]