Mankind will in time discover that unbridled majorities are as tyrannical and cruel as unlimited despots.Actually, Adams and his contemporaries were well-versed in classical history and were no doubt familiar with the cruelty of "unbridled majorities" of the past that ruled the assemblies of Greek city-states. Adams enjoyed the writings of Thucydides, chronicler of the Peloponnesian War so would be familiar with the events outlined by Victor Davis Hanson in A War Like No Other: How the Athenians and Spartans Fought the Peloponnesian War (p. 102).
Meanwhile, once these Athenians got into their collective minds to butcher, butcher they did, whether the citizenry of Melos or old Socrates, with impunity. Under the laws of Athenian democracy there was neither an independent judiciary to strike down a popular decree as unconstitutional nor a sovereign and immutable body of constitutional law protecting human rights and proscribing the powers of the assembly. Athens' conduct during and right after the war--whether killing Mytileneans, Melians or Socrates--was all done according to majority vote, besmirching the reputation of democracy itself for centuries to come. Almost every savage measure taken by generals in the field was either preapproved by the sovereign Athenian assembly or understood by fearful commanders to be in line with the harsh dictates of an unforgiving voting citizenry back home.The brutality resulting from Greek direct democracy is a powerful reminder of the necessity of the rule of law to protect the rights of the minority from the whims of the majority. This includes the ultimate minority: the individual. To quote my libertarian friend McKay: "I'm a minority and my rights are being violated." This is why the subversion of rule of law to reward favored parties by depriving others' of their property should set every one on edge. The GM and Chrysler bankruptcies come to mind in this regard. Also, demagoguery against bankers or other specific segments of industry just because most people think they are "greedy" sets off alarm bells. Fortunately, we have many checks on the power of the majority such as the presidential veto, judicial review and the filibuster, as Don Boudreaux from Cafe Hayek elaborates here.