Trump rally violence reflects badly on everyone involved, but most of all on Trump

In the coverage of the event, (or should it be called a non-event, since it was canceled?), there is plenty of blame and criticism to go around.
 I'm all for vigorous political expression, for enthusiastic rallies. I'm entirely against any efforts by one side to suppress the political expression of those who disagree.
Of all the coverage of the activity, I found the Guardian coverage from the UK to be the most balanced and accurate.
 NO ONE had their freedom of speech trampled; the right to free speech is exclusively a right to freedom from GOVERNMENT restriction or obstruction of speech. It does not extend to any other entity behaving so as to impede expression, but that doesn't make it acceptable for individuals or groups of people to shut down or prevent political expression. We are a nation that prizes persuasion not thuggery, or at least, we should be.
It is worth noting that Donald Trump (and VP candidate Sarah Palin before him, the right seems chronically unclear on this point) is unclear on the important distinction of what is a right, and what is a value. From the Guardian:

Scuffles broke out between Trump supporters, protesters and police, and a number of arrests were made, including of at least one reporter. As the mayhem took hold, Trump was reduced to complaining about the situation on the air, telling MSNBC: “It’s sad when you can’t have a rally. Whatever happened to freedom of speech?”

NOTHING happened to freedom of speech. The police did everything they should have done; government promoted free speech by attempting to allow both sides to express themselves. Those who behaved violently, on both sides, were wrong, were bad, but were not interfering with freedom of speech either. But they contributed NOTHING to political expression other than an example of how not to behave.

Police walked up and down the arena stairs holding sheaves of plastic handcuffs amid fraught but as yet non-violent scenes. Attendees grabbed signs from each other’s hands and several dozen people were ejected from the event long before formalities were scheduled to begin. At least one section of young people was cleared out by police long before the event began, including many of Middle Eastern appearance. “Just because I look like them doesn’t mean I’m with them,” said one.

I condemn Bernie Sanders supporters if they were involved. We don't know, given conservative dirty tricks, how many Sandser supporters were genuinely involved, and who might have been paid provocateurs from Trump rivals. It should be sufficient to condemn both. It is also important to condemn the conservative admiration of such violence that makes it a desideratum, in a way which is not found on the left.

There is a growing catalogue of violence at Trump events. In the past week alone an attack on a non-violent protester led to criminal charges against a Trump supporter, and Michelle Fields, a reporter for conservative website Breitbart, was allegedly assaulted by Corey Lewandowski, Trump’s campaign manager. Trump’s rhetoric has done little to keep it in check. When the Republican frontrunner appeared in St Louis earlier on Friday, for an event that entailed more than 30 arrests, he complained: “Part of the problem and part of the reason it takes so long [to kick protesters out] is nobody wants to hurt each other any more.” Trump added: “There used to be consequences. There are none any more. These people are so bad for our country. You have no idea folks, you have no idea.”

Trump has also asked his supporters from his podium to hurt people, and expressed his own desire to punch a protester in the face. That was not the only incident where Trump endorsed and encouraged violence against those who disagreed with him, including falsely representing the NON-violent protester as deserving violence.

“Here’s a guy, throwing punches, nasty as hell, screaming at everything else, when we’re talking,” Trump told the crowd, although CNN reported the man did not appear to be fighting with security officers. “The guards are very gentle with him. He’s walking out, like, big high-fives, smiling, laughing,” Trump continued, before saying to loud cheers: “I’d like to punch him in the face, I tell ya.” The incident was the latest in a string of controversial comments by Trump regarding protesters at his rallies. In November, after a Black Lives Matter protester was beaten and choked after disrupting a rally, Trump appeared to condone the rough treatment. “Maybe he should have been roughed up, because it was absolutely disgusting what he was doing,” he said on Fox News at the time.

From another Guardian account, this one detailing the personal experience of one of their reporters:

The Trump campaign has tried write off rally violence as something he didn’t sanction, but now his campaign manager has manhandled a reporter
...The incidents are piling up. A Black Lives Matters protester was sucker-punched by a white bystander at a rally in Fayetteville, North Carolina. A young black woman was surrounded and shoved aggressively by a number of individuals at a rally in Louisville, Kentucky. A black protester was tackled, then punched and kicked by a group of men as he curled up on the ground in Birmingham, Alabama. Immigration activists were shoved and stripped of their signs by a crowd in Richmond, Virginia. A Latino protester was knocked down and kicked by a Trump supporter in Miami.
...
The Lewandowski incident and the one at Radford feature the assault of the press, not the assault of protesters, but both types of violence are of a piece: they are about silencing voices of dissent, silencing critics, silencing truth in a campaign built around racist fear-mongering and bombast.
And that – it shouldn’t need to be said, but it does – is undemocratic. Activism and the media play a vital role in any healthy democracy, and to allow this kind of brutality and silencing of free speech to go unaddressed is worse than undemocratic: it’s fascist.

Again, like the Chicago example, where the Trump campaign lied about conferring with law enforcement, the Trump campaign also lied about the involvement of Radford University, which had little hands-on involvement with that Trump rally. This underlines a pattern of behavior, of refusing appropriate accountability, that does not bode well for someone who thinks they can be a leader.
While I do not condone the Sanders protesters for attempting to shut down the Trump rally, as distinct from protesting against it, the Sanders protester criticism was apt. Again, from the Guardian article:

After the postponement was announced a Trump campaign statement said: “Mr Trump just arrived in Chicago and after meeting with law enforcement has determined that for the safety of all of the tens of thousands of people that have gathered in and around the arena, tonight’s rally will be postponed to another date. “Thank you very much for your attendance and please go in peace.” Despite Trump’s statement that he had consulted law enforcement, the Chicago police department emphasised it had no involvement in the decision."

and

As one, Violet Ornelas, 28, gleefully told the Guardian: “If he can’t even handle Chicago, what makes him think he could handle Isis?”

Shame on Trump for creating the violence on his side, for hiding behind the police for his decision - the coward, and for failing to understand that political protesters in the USA, or in formulating foreign policy, the decision to de-escalate rather than escalate violence is always important. That is a lesson Trump supporters need to learn as well.