This section from Reinhold Niebuhr’s Moral Man and Immoral Society: A Study in Ethics and Politics strikes me as quite true:

The coercive factors, in distinction to the more purely moral and rational factors, in political relations can never be sharply differentiated and defined. It is not possible to estimate exactly how much a party to a social conflict is influenced by a rational argument or by the threat of force. It is impossible, for instance, to know what proportion of a privileged class accepts higher inheritance taxes because it believes that such taxes are good social policy and what proportion submits merely because the power of the state supports the taxation policy. Since political conflict, at least in times when controversies have not reached the point of crisis, is carried on by the threat, rather than the actual use, of force, it is always easy for the casual or superficial observer to overestimate the moral and rational factors, and to remain oblivious to the covert types of coercion and force which are used in the conflict.

This obfuscation of motives is part of what differentiates charity from taxation. True charity cannot be coerced.

See also: Reinhold Niebuhr Today, ed. Richard John Neuhaus (Grand Rapids: Eerdmans, 1989).