Yesterday morning, Cory Booker, the Democratic senator from New Jersey, went to the Emanuel African Methodist Episcopal Church in Charleston, South Carolina, where, four years ago, white supremacist Dylann Roof fatally shot nine people at a Bible study class. (Roof is not insane. He was found guilty of murder and has been sentenced to death.)

Booker delivered a speech addressing white nationalism and gun violence in sweeping, often poetic terms. Booker began by talking about the “profound contradiction” at the founding of the country, the establishment of a democracy at a time when blacks were counted as three fifths of a person. But his intent was not a history lesson; rather, he wanted to strike an uplifting and unifying message in tone and substance evocative of Barack Obama, who spoke at the church in the wake of the killings in June 2015.

Obama is a hard act to follow, but Booker certainly hit his stride yesterday. For a candidate whose frequent references to “love” and “unity” seem misplaced in a time of political acrimony, he was able to tie that message to the demands of the moment. It is not enough, he said, to not be a racist. One must be “antiracism”, he said. In that sense, silence is unacceptable and “to be passive is to be complicit”.

Booker shunned the notion of “tolerance”: we are “not called to tolerate injustice”, he explained. He railed at those who are indifferent towards others, who harbour the “dangerous delusion some are outside our moral concern”. Without mentioning Donald Trump’s name, “from the highest office” is how he made reference to the President, Booker excoriated those using language that stokes hysteria about an “invasion” and calls minority cities “infested”.

But his audience was wider, and his finger pointed at a party and society that allows Trump to propagate hate and racism. He insisted the issue is not who is a racist, I would argue it is not “only” who is a racist, for it is critical to call Trump out for what he is, but “who is and isn’t doing something about it”.

Booker asked: “Do you want to contribute to our progress or through apathy and indifference to the violence that threatens to tear us asunder?”

He declared that you are “either an agent of justice or you are contributing to the problem”. In an indirect attack on Trump and his legions of self-described patriotic followers, Booker said, “Patriotism is love of country. But you can’t love your country unless you love your fellow countrymen and women, all of them ... You cannot lead the people if you don’t love the people.” Arguing that this is an issue of national security, Booker continued with a list of potential legislation, including a ban on assault weapons, gun-licensing reforms, an assessment of domestic terrorism and improved tracking of hate crimes.

We have shown greatness, he urged, not because of the absence of violent bigotry and white nationalism, but “by our efforts to overcome them”.

Rejecting the notion that America is a tale of rugged individualists, he emphasised the story of collective efforts to emancipate slavery and end Jim Crow, to give women the right to vote and to improve labour conditions. He urged us to now “reaffirm our common bonds”.

In short, he made the case that, without love of one another, we cannot solve our problems or even keep us safe. He called on everyone to be “freedom fighters” and “put more ‘indivisible’ back into our ‘one nation under God’.”

Booker’s rhetoric can sometimes overwhelm him, but in this case he grasped the importance of the moment.

His argument, moreover, is essentially that Trump is unfit to lead because he is incapable of loving and serving all Americans, unarguably true, and that Republicans, the right-wing media, including Fox News, conservative apologists and the rest do not get off scot-free by proclaiming they are not racists.

They are plainly part of the problem, a critical part of Trump’s support system.

And to the larger audience, politically nihilist voters who say both parties are the same, or mainstream media that treat Trump as a normal president, Booker’s words should hit home.

They, too, are part of the problem. You are either invested in throwing out Trump and combating Trumpism, or you are enabling it. Whether Booker becomes the nominee or not, his speech is an important one that we all should take to heart.

• Jennifer Rubin writes reported opinion for The Washington Post