An overwhelming majority of Americans say they believe protests against unfair government treatment make the United States a better country.

Unless, that is, the protesters are black.

A new Public Religion Research Institute poll asked whether protests against government mistreatment always improve the country, and a full 67 percent of white Americans strongly or at least partially agreed. But when it asked a separate sample whether black Americans protesting government mistreatment always makes the country better,  just 48 percent of white Americans agreed.

That's two-thirds, versus less than half.

And the racial differences didn't end there. In fact, non-white Americans are more likely to believe in the benefits of black Americans protesting Americans writ large. Among non-white Americans, 56 percent agreed that protests against government mistreatment are good for the country, but a full 65 percent said the same when the people protesting were black.

The gaps, as the chart below shows, are clear and remarkable.

“We expected to see some differences along racial lines when we asked these questions, but we certainly had not expected a gap that size, a gap that large,” Dan Cox, research director at Public Religion Research Institute, told me.

White Americans made up the lion's share of those polled in the survey — 709 of the 1,007 people surveyed. Pollsters also talked to 109 black Americans and 121 Latinos for the same survey. Those who responded were asked about range of issues shaping the country, including religion, race, language, patriotism and immigration.

Pollsters often worry that the people contacted for surveys will, because they are human, give in to the instinct to give the “right” or “admirable” answer rather than an honest one, Cox told me. They call this phenomenon the "social desirability bias." And that bias certainly makes the work of polling  challenging.

To subvert this problem, the PRRI asked a randomly selected half of the 1,007 people polled the question about whether protests against government mistreatment always improve the country. They asked the remaining half whether protests against government mistreatment by black Americans always improve the country. And the results were clear.

“Most white Americans generally believe that protests are good for the country, but they hold significant reservations about protests led by African Americans,” Robert P. Jones, chief executive of the Public Religion Research Institute, said in a statement released Tuesday along with the polling data. “Among white Americans, strong support for protesting government mistreatment drops dramatically when protesters are identified as black Americans.”

The PRRI/RNS Religion News Survey was conducted by the nonpartisan Public Religion Research Institute in partnership with Religion News Service. The nationwide survey of 1,007 adults was conducted from June 10 to June 14, 2015, in English and Spanish.

The date range of the poll is significant because pollsters finished their work three days before a white gunman fatally shot nine African Americans in a Charleston church, setting off a new round of public debate about race and mistreatment and protests against the Confederate flag in South Carolina. But those polled would, quite probably, have been aware of recent events in Ferguson, Mo.; New York City, North Charleston, S.C.; and Baltimore that led to large protests.

In each of these cities, largely black (but certainly not exclusively black) groups of protesters took to the streets. Some marched in support of a growing national movement organized loosely around the slogan "black lives matter." In two of these cities, protests at points grew violent and devolved into riots. In Ferguson, police used military equipment, including tanks, to try to corral and quell protests, even before rioting or looting erupted.

Cox thinks that it is quite likely that protests against alleged police misconduct and excessive use of force were on the minds of those polled by the Public Religion Research Institute in June. But he also thinks that it was not simply the protests themselves but the way they were covered that might explain the nearly 20-point gap in the way that white and non-white Americans view the effect of protests involving black Americans.

News coverage of the protests and later rioting in Baltimore focused far more attention on the burned CVS store and disrupted sports events than on more complex and less visual issues such as the array of social and economic disparities that have created pockets of deep poverty in predominantly black neighborhoods in Baltimore.

What is clear is that Americans who generally support protests against government mistreatment aren't nearly as supportive if the ones doing the protesting happen to be black.