As for Mr. Walsh, to me he embodies much that has gone wrong in American politics, just like the man he is challenging. The democratic virtues we desperately need to reclaim in American public life — moderation and compromise rightly understood, civility, forbearance — are antithetical to Mr. Walsh. So is any apparent self-awareness of the fact that at best we are in possession of partial truths.

Even more troubling is that the rhetoric Mr. Walsh has long deployed is racist, bigoted, vicious, threatening and dishonest. A man of pulsating rage, he seems to have viewed first his public office and then his radio program as a forum to vent, to perform, to hurt, to wound.

I understand why some conservative critics of Mr. Trump are promoting Mr. Walsh’s candidacy; they see him as a means to inflict injury on the president, including as a way to psychologically “trigger” him. But rallying around Mr. Walsh, even if only for the purposes of weakening and disorienting Mr. Trump, strikes me as unwise, particularly with a far more responsible person like the former Massachusetts governor William Weld already in the race.

Mr. Walsh is about as imperfect a vessel as you can imagine for challenging Mr. Trump in a primary campaign, since he was in many ways a proto-Trump. What kind of inhumane person mocks the parents of children killed in the Sandy Hook massacre because they sue gun manufacturers, which is what Mr. Walsh did in 2017? He tweeted, “I’m sick and tired of the Sandy Hook parents. They’re partisan and political. They can be attacked just like anyone else.” In another tweet, he added, “Sandy Hook parents: Your 15 minutes is up.”

At certain times, embracing the ethic that the enemy of my enemy is my friend can be justifiable, but it is always morally fraught. And what exactly might Mr. Walsh’s appeal to Trump voters be? If they want to support a provocateur who makes racially incendiary comments, they already have their man in the Oval Office.

One thing Mr. Walsh does have that the president does not is the ability to apologize. Whether one believes his apology is sincere or an affectation, the product of genuine remorse or opportunism, an exchange on Monday between Mr. Walsh and MSNBC’s John Heilemann is worth watching: Mr. Walsh speaks candidly about how his differences with various people over policies led him to say things that were, as he put it, “horrible.”

In that sense, Mr. Walsh is a cautionary tale. We live in a time of acute bitterness and acrimony, where people’s first (and second and third) impulse is to brutalize, insult, embarrass and demean those who hold different views. The purpose of language, as they see it, isn’t to clarify or enlighten or reason together. It is to inflict the maximum pain possible on other human beings.