The odd one out among the principles supporting democracy is 'majority rule', as it can lead to 'tyranny of the majority' without the protection of minority rights, unlike free and fair elections, dignity of the individual, and equal treatment before the law which are fundamental to democratic governance. So, the correct option is C.
In the context of assessing democracy, among the options provided, the odd one out in ensuring democratic principles is C. majority rule. Democracies need to ensure free and fair elections (A), protect the dignity of the individual (B), and uphold equal treatment before the law (D). While majority rule is a principle of democracy in terms of decision-making, without the protection of minority rights, it can lead to a 'tyranny of the majority', where the majority's will is enforced without regard to the rights of those in the minority. This is why the maintenance of individual dignity and equal legal treatment are also core to the functioning of a democratic system.