Deary, deary me.
We might be prone to be sympathetic to the Roman assemblies, and certainly its members were not nearly as powerful as the senators. The problem, however, is that democracies then as now can be manipulated by demagogues, sometimes even those with dictatorial ambitions (as we saw in the 2004 election). This was what helped Julius Caesar rise and overthrow the republic. The constitutional balance between the democracy and the aristocracy was what prevented a tyrannical leader, with no one's interest in mind other than his own, from seizing power. The point of any constitutional system is to place checks and balances so that no source of authority (executive, aristocratic, or democratic) can achieve unchecked power. For this, look no further than our constitution. Our constitution is designed so that, say, some 52% majority can't just invalidate the equal protection clauses in the constitution and thus deny rights, say marriage rights, to some unpopular minority group.[snip]
In effect, Tiberius used the same theory of popular sovereignty that Julius Caesar would later use, and that the supporters of Prop 8 in California used. The theory, that laws and constitutional mandates can simply be ignored when popular majorities disagree with them, was (is) repugnant to the genius' of both the Roman and American constitutional systems, and if carried to their logical ends, would put the state under the absolute control of any temporary popular majority. Replace "popular majority" with "president", and you get Nixon's famous decree that "if the president does it, that means it is not illegal".
He makes a good case that following the popular will without respecting minority rights can weaken and eventually topple a democracy. Go have a read. It's another good arrow to have in the quiver.