Last Tuesday Corey Lewandowski, Donald Trump’s former campaign manager, was challenged on television about a 10-year-old girl with Down’s syndrome who was separated from her mother at the Mexican border and put in a detention centre. As a Democratic strategist cited the case, Lewandowski mocked the girl’s plight, imitating the sound of a sad trombone. “Womp womp,” he said.

Three days later, the White House press secretary, Sarah Huckabee Sanders, was asked to leave the Red Hen restaurant in Lexington, Virginia, because of the policies of the administration she represents. “I explained that the restaurant has certain standards that I feel it has to uphold, such as honesty and compassion and cooperation,” the owner, Stephanie Wilkinson, told the Washington Post. “I said, ‘I’d like to ask you to leave.’”

An aggrieved Sanders later tweeted: “Her actions say far more about her than about me. I always do my best to treat people, including those I disagree with, respectfully, and will continue to do so.”

When it comes to matters of civility in political discourse, the Trump administration and its advocates are in no position to preach: any plausible claim they may have staked for the moral high ground was torched very early on. Trump made a Pocahontas joke while addressing Native American servicemen; called protesting black football players “sons of bitches”; and, on Monday, tweeted that a black Congresswoman, Maxine Waters, was “an extremely low IQ person”. Having laid waste to decorum, tradition, convention and sensitivity, his administration should not be surprised when people respond in kind.

We do not need to reserve opinion on what Trump is capable of. The time to pull the emergency brake is now.

The issue here goes beyond etiquette. Both during his campaign and in office, Trump has violated basic democratic norms. He has encouraged violence at his rallies, said he may not accept the election result if he lost, and thanked African Americans for not voting. In office he has threatened to pardon himself if prosecuted; employed his family in key positions while authorising small children to be taken from their own families; endorsed and supported an alleged paedophile for the Senate; drawn an abhorrent equivalence between neo-Nazis and anti-fascist protesters; called for due legal process to be denied to immigrants; advised police to physically abuse suspects; and, as upheld by the supreme court on Tuesday, barred people from several Muslim countries from entering the US.

This is not just another president, with whom one may have honest disagreements: it is a brazenly dishonest man who routinely and openly uses misogyny, xenophobia and racism as political tools. Not so long ago, Republicans also claimed Trump was unfit to be president. Some still do.

It makes little sense to prostrate oneself at the altar of civility while others are gleefully desecrating democracy itself. Historical precedents abound where people, in retrospect, feel they should have done more when they had the chance. We do not need to reserve opinion on what Trump is capable of before we get to the end of this sordid journey. The time to pull the emergency brake is now. We have seen enough.

As acts of resistance go, this week’s at the Red Hen could hardly have been less impulsive or more mild. The chef noticed Sanders and called Wilkinson at home to say the staff were concerned and to ask what they should do. Wilkinson drove to the restaurant and consulted the staff. Many are gay, and were offended by her defence of the transgender ban in the military. They were also unimpressed by her evasion of questions on the child separation policy. They said they wanted Sanders to leave. Wilkinson asked her out on to the patio, while her party of around eight were on their cheese plates, and carried out their request. It may not have been civil, but it was certainly cordial. Sanders’ party offered to pay for what they had eaten. Wilkinson told them it was on the house. Womp womp.

While parents on the Mexican border are being told their kids are being taken for a bath only to find they have been abducted by the state and detained alone, there is only so much sympathy I can have for someone who actively promotes that policy from being inconvenienced in her dinner plans.

Of course, the right has claimed victimhood, as though Sanders were some latter-day Rosa Parks. This should come as no surprise. A sense of grievance is central to its political identity. Out-traded by China, soon to be outnumbered by minorities, outmanoeuvred on the battlefields of the Arab world, Trump’s base nurses its resentments. A study in April suggested it was not economic anxiety that prompted white, Christian men to vote for him, but that “their dominance as a group was under threat”.

When they have nothing to be aggrieved about, they attach their wounded self-image to imagined slights, regardless how bizarre. Some believe Obama is a Kenyan-born Muslim terrorist, others that Hillary Clinton was involved in a child sex abuse ring in a Washington pizzeria.

This victim mentality is, of course, closely tied to an entitlement to violent retribution. Across the country, restaurants that carry the name Red Hen (it’s not a chain) are being threatened with boycotts and burning by people who would ordinarily support a business’s right to deny service to whomever it wants (particularly if they’re gay and want a wedding cake).

“I’m not a huge fan of confrontation,” Wilkinson told the Post. “I have a business, and I want the business to thrive. This feels like the moment in our democracy when people have to make uncomfortable actions and decisions to uphold their morals.” Her actions were brave, but they pose no great challenge to political morality. There is no parallel here with a restaurateur refusing service to black or gay customers: Sanders was asked to leave not because of who she is but for what she has done. She was told her entourage could stay.

Ordinarily one might argue that there should be no ideological obstacle to a government representative eating in a place of their choice. Elected representatives and their appointees, arguably, hold a legitimacy that should afford them free passage in public places. We wouldn’t want to live in a world where certain restaurants are off limits to people from mainstream parties. But, for reasons outlined above, these are no ordinary times.

The question of where one draws the line on these matters is a legitimate one. But we should not be in any denial that there is always a line. If a group of fully robed Klansmen or neo-Nazis in full regalia walked in, some liberals would be far less squeamish about removing them. The question has never been whether you draw a line between what is and is not acceptable, but where you draw it. Trump crosses that line routinely – stoking divisiveness, encouraging enmity and violating basic human values in policy and pronouncement. This moment calls not for civility but civil disobedience.

• Gary Younge is a Guardian columnist