If Dylann Roof, the white supremacist who allegedly massacred nine congregants at a black church in Charleston, wants a race war, he's got one.

So wrote Vester Flanagan in a rambling, at times barely coherent, manifesto explaining why he murdered two white journalists during a live news broadcast, before he turned his gun on himself.

Describing himself as "somewhat racist" against blacks and Latinos as well as whites, and complaining he had been bullied by other black men because he was gay, Flanagan's motives are more convoluted than Roof's. Perhaps trying to interpret the voices inside a madman's head is a fool's errand.

That doesn't make the Twitter chatter emanating from some presumably saner people any less disturbing. In the aftermath of the Roanoke shootings, some posted that this is what happens when you get blacks all worked up about racism (that is, when the posters weren't devolving further by saying this was typical violent black behavior).

Others accepted Flanagan's claims to have been discriminated against uncritically, even implicating his victims. A couple even coldly wrote, "Racist lives don't matter."

Random commenters on the internet aren't representative of much, as all of us in online media try to remind ourselves daily. Social media platforms are also frequently used to blow off steam, and, in emotional times, posters sometimes write things they haven't had time to think about or that they don't really mean.

But there is enough hate, and even more misunderstanding, going around that such sentiments cannot be dismissed entirely.

In the days leading up to Roanoke, there was a great deal of commentary speculating that Republican frontrunner Donald Trump was the successor to George Wallace. On cue, David Duke endorsed him (with qualifications). Even some conservatives wondered if Trump was mainstreaming white identity politics.

Despite his frequently off-putting and ill-considered comments on racially sensitive issues, my sense is that Trump isn't consciously trying to be that kind of candidate. But a small slice of his supporters would certainly like him to be.

Is there any market for that kind of politics in the multicultural America of 2015?

If all politics were local back in the days of Tip O'Neill, all politics are identity politics today. Sarah Palin was as much a cultural identity figure as a political one. The video with which Hillary Clinton launched her campaign was more about the identities of the Democratic base than her own candidacy.

None of this has to be racial, much less racist. Many voters attracted to Trump would also be enthusiastic about electing Ben Carson the second African-American president, to cite just one example. But in a country where racial divisions often coincide with profound differences in outlook, it isn't hard to see how these trends can turn into something uglier.

Consider: America has an aging, shrinking white majority that in the foreseeable future will become another minority. The symbols and Founding Fathers they once revered are being critically reappraised in light of their more complicated meaning to some members of the growing demographic groups, who identify more strongly with the history of slavery and the displacement of Native Americans.

At the same time, many black Americans feel as insecure in their rights and their persons as they did in the heyday of political figures like Wallace. They don't see the deaths of young blacks in police custody under disputed circumstances as isolated incidents. They don't take it as a given that either the country's political leaders or the white majority believes that black lives matter.

Moreover, all this is happening at a time when U.S. race relations get further from white and black, as the country admits millions of immigrants who don't necessarily identify as white but also had nothing to do with discrimination against blacks.

You can minimize or even mock these racial anxieties, which are certainly not universally felt by whites, blacks, or anyone else. That won't make them go away. Some Americans feel dispossessed while others don't see the country as ever being truly theirs in the first place — both enormous challenges that cry out for responsible political leadership.

Where is that leadership? The latter concern is manifested by Black Lives Matter. Trump isn't yet an expression of the former. But someday somebody smoother than Duke and even more demagogic than Trump will ask where the non-Latino white equivalent of the NAACP or La Raza is. How will the leadership of a 90 percent white GOP answer?