Extremism is any ideology

Ideology

An ideology is a set of ideas that constitutes one's goals, expectations, and actions. An ideology can be thought of as a comprehensive vision, as a way of looking at things , as in common sense and several philosophical tendencies , or a set of ideas proposed by the dominant class of a society to...

 or political act far outside the perceived political center of a society; or otherwise claimed to violate common moral standards

Morality

Morality is the differentiation among intentions, decisions, and actions between those that are good and bad . A moral code is a system of morality and a moral is any one practice or teaching within a moral code...

. In democratic

Representative democracy

Representative democracy is a form of government founded on the principle of elected individuals representing the people, as opposed to autocracy and direct democracy...

 societies, individuals or groups that advocate the replacement of democracy with an authoritarian

Authoritarianism

Authoritarianism is a form of social organization characterized by submission to authority. It is usually opposed to individualism and democracy...

 regime are usually branded extremists, in authoritarian societies the opposite applies.

The term is invariably, or almost invariably, used pejorative

Pejorative

Pejoratives , including name slurs, are words or grammatical forms that connote negativity and express contempt or distaste. A term can be regarded as pejorative in some social groups but not in others, e.g., hacker is a term used for computer criminals as well as quick and clever computer experts...

ly. Extremism is usually contrasted with moderation, and extremists with moderates.