The fact that americans disagree over whether eavesdropping on domestic phone conversations by federal antiterrorism investigators is necessary for security or a threat to democratic values demonstrates which "pillar" of democracy?

social, economic, and political pluralism

Pluralism is the notion that in liberal democracies power should be distributed among a variety of economic and ideological pressure groups and should not be held by a single elite or group of elites as this could result in tyranny