The activists at University of Illinois-Chicago, where Trump had scheduled a rally, effectively shut it down yesterday. When the rally was abruptly canceled at the last minute, Trump supporters and protestors clashed. Several people were injured.

This brief video puts the events of last night into some context of Trump’s escalating remarks at recent rallies (12:50 with a :30 advertisement at the beginning):

As this timeline created by Maddow’s production team illustrates, the rhetoric of Donald Trump is escalating and is now, pretty plainly, inciting violence among his supporters. Trump’s hate-filled rhetoric reaches beyond his rallies. Just two weeks ago, white high school students attending their school’s basketball game chanted “Trump, Trump, Trump” as way to intimidate their mostly Latino opponents on the other team.

What the clip by Maddow doesn’t mention is the way that mainstream news outlets, including MSNBC which airs her show, are complicit in this. The television news outlets give Trump free air time because it is good for their ratings. And, of course, it benefits Trump’s campaign. According to one estimate from January this year, Fox News alone has given Trump the equivalent of more than $30 million in free air time.

Because these events happened in Chicago at an event related to a presidential campaign, many people in the US were reminded of the violence against protestors at the 1968 Democratic Chicago convention. While this became a turning point in American politics, I don’t think this is the most apt comparison.

I think that Trump’s candidacy, and the appeal to his supporters, speaks to a much more sinister comparison. As Brent Staples, writing at the New York Times, recently pointed out, Trump’s rhetoric harkens back to reconstruction era politics. Here is Staples, and it’s worth quoting him at length:

Antigovernment and militia groups have grown rapidly since 2008. Shortly after Mr. Obama’s election, the Southern Poverty Law Center, which monitors extremist groups, reported that the antigovernment militia movement had undergone a resurgence, fueled partly “by fears of a black man in the White House.” And for proof of violence like that of the Reconstruction era, look no further than the young white supremacist who is charged with murdering nine African-Americans at a church in Charleston, S.C., last summer.

This is the backdrop against which Donald Trump blew a kiss to the white supremacist movement during a television interview by refusing to disavow the support of the white nationalist and former Ku Klux Klan leader David Duke. Republican Party leaders in Congress wagged their fingers and delivered pro forma denunciations. What they need to understand is this: Racial hatred is a threat to the country and their party’s leading candidate is doing everything he can to profit from it.

That’s what Donald Trump is doing with this increasingly violent and hate-filled rhetoric, he’s “blowing a kiss to the white supremacist movement.” This is the GOP frontrunner and presumptive nominee for president of the US. These are dire times.

What the protests at the rally last night in Chicago showed is that it is possible for people to stand up against the bigotry and hatred of Trump and his supporters. It’s not just possible, it’s necessary.