The leaders and backers of the Yanukovych regime in Ukraine and the Maduro regime in Venezuela have had a ready answer. The demonstrators are fascists, neo-Nazis and criminals.
Russian President Vladimir Putin's sidekick, Prime Minister Dmitry Medvedev, called the demonstrators "masked and armed people" with "black masks and Kalashnikov rifles" using "terrorist methods."
Backers of the Venezuelan regime, headed by Hugo Chavez's chosen successor, Nicolas Maduro, say that the street demonstrators are selfish rich people and fascists trying to launch a coup d'etat.
Others see the crowds differently. Timothy Snyder and Anne Applebaum, distinguished historians of Eastern European, stress that the Ukrainian protesters include Russian as well as Ukrainian speakers, people on the political Left as well as the Right, Christians and Jews and Crimean Tatars.
In Venezuela, the New York Times reports, protesters include many with modest incomes, frustrated with horrific violent-crime rates, people worried not about investment portfolios, but about shortages of milk and toilet paper.
From a distance, it's impossible to gauge the motives and backgrounds of all the protesters, and surely there are among them some whom almost all Americans would consider repugnant.
But it's noteworthy that they are taking grave risks -- dozens died in Kiev's Maidan Nezalezhnosti and many have died in Venezuela cities -- to oppose governments with roots in the political Left.
The protests against Yanukovych began when he shifted away from the European Union and toward Russia's Vladimir Putin, who characterized the dissolution of the Soviet empire as the greatest tragedy of the 20th century (a title for which there is vigorous competition).
In Venezuela, Chavez and Maduro embraced socialism, with the state taking over oil operations and revenues, and vigorously proclaimed their support for Fidel and Raul Castro's Communist Cuba.
American mainstream media, nostalgic for Vietnam War protests, tend to regard protests as the province of the political Left.
They hailed the Occupy Wall Street encampments, despite their violent crime and gauzy pronouncements, as heralding an uprising of the virtuous 99 percent.
Despite such encouragement, Occupy fizzled and polls showed that the demand for redressing "income inequality" was so weak that, contrary to advance word, President Obama scarcely mentioned the phrase in his State of the Union address.
Certainly the protesters in Ukraine and Venezuela are not seeking the left-wing goal of income redistribution. The Ukrainians are not seeking a larger welfare state, and the Venezuelans have learned from hard experience that Chavez's policies produced not redistribution, but economic destruction.
But you run up against a paradox if you see the demonstrations as a demand for electoral democracy. In Ukraine, they resulted in the ouster of a leader who was in fact elected.
Chavez and Maduro also won elections, though there is plenty of evidence of fraud and intimidation.
I think it's more helpful to see the protesters as rebelling against the absence of the rule of law.
Ukraine, like Russia, saw the gobbling up of state property by oligarchs in the 1990s. Venezuela has seen the destruction of a free press and systematic plundering of the private sector. Both have seen leaders tearing up constitutions.
And the protesters can see in their own neighborhoods alternatives to Yanukovych's patrons in Russia and Chavez's and Maduro's beloved Cuba.
Ukrainian protestors waved the European Union flag and undoubtedly envy the success of EU (and NATO) neighbors Poland and Slovakia in creating thriving economies underpinned by the rule of law.
Venezuelans (at least until Maduro jammed Colombian TV) have nearby the example of Colombia, which subdued the narcoterrorist FARC guerrillas and now is enjoying economic growth and the rule of law as well.
Unfortunately, it may be as difficult for protesters to reach these goals as it has been for those who flocked to the squares in the Arab spring.
Ukraine still suffers from Soviet-era lassitude and fatalism, and Venezuela from the curse of supposing oil deposits guarantee a comfortable life.
Russia may still move into Ukraine's Russian-speaking Crimea and industrial east. Castro goons may keep killing in Caracas.
The rule of law is hard to establish and easy to dismantle. Something to keep in mind as our president keeps unilaterally rewriting Obamacare and our IRS targets his political opponents.