The president of a synagogue in Charlottesville, Va., described the scene.

“For half an hour, three men dressed in fatigues and armed with semiautomatic rifles stood across the street from the temple,” wrote Alan Zimmerman, the president of Congregation Beth Israel. “Several times, parades of Nazis passed our building, shouting, ‘There’s the synagogue!’ followed by chants of ‘Sieg Heil’ and other anti-Semitic language. Some carried flags with swastikas and other Nazi symbols.”

Although he indicated that the local politicians and police did not take seriously his expression of his concerns before the protest, Zimmerman said the Charlottesville community — Jewish or not — came together in profound ways for the synagogue. For example, a Navy veteran stood watch over the synagogue during Shabbat services on Friday evening and Saturday morning, and at least a dozen complete strangers stopped by the synagogue to ask whether the congregants needed assistance.

This Navy veteran knows what President Trump did not, and still does not, know. There is a real threat to the United States in not standing up to those who would denigrate people who do not fit their scheme of what the appropriate religion, creed, color or national origin should be.

It takes all of us pulling together to create a society that welcomes everyone. That includes standing up to those who would denigrate others. Mr. Trump has thus far failed that test.

One lesson to contemplate is that none of us makes it without all of us. Even the wealthy businessman who thinks he has achieved everything on his own has been aided by others in his rise up the ladder of success.

He must depend on others: his customers, his partners, his stockholders, his employees, and the government that has provided security, transportation for goods, medical research, and so many other goods and services without which no one could be successful.

For every white Southern peanut farmer, there is a George Washington Carver, the African-American biologist who promoted the use of the peanut and helped make that farmer successful. Carver also developed techniques to improve soils depleted by repeated plantings of cotton.

For all his scientific contributions, he endured the continual interruptions of racism. Yet he undoubtedly helped the ancestors of many of the Confederate and Nazi sympathizers in Charlottesville.

Carver’s lesson of perseverance is one lost on Mr. Trump. He cannot be bothered to know the many lessons of American history.

There are those who wish ill of others because of religion, race, national origin, etc. Witness the chants in Charlottesville of “Jews will not replace us” and “Blood and soil,” the latter a famous Nazi chant.

Mr. Trump, you must stand up for what is right. What is right is the opposite of what was demonstrated by the Nazi and Confederate sympathizers. Their overt racism and anti-Semitism must be rejected by not just the readers of this paper, but by everyone in a position of influence and power.

I doubt Mr. Trump would like to be associated with the three magazine covers of national and international publications showing him using a Nazi salute or the KKK hood. But unless he changes his ways, he will be forever associated with those images.

I recognize it will be difficult for him to change his ways. He has shown racist activities and attitudes throughout his history. He has used the con to get his way throughout his business career.

But unless he changes, he will go down as an unsuccessful and futile president. I just hope that he does not take the rest of us with him.

We must oppose his current efforts and tactics at every turn. He must never get a free pass from any Jewish group. We must hold him accountable.

Every time he and his Justice Department allow restrictions on voting rights, we must oppose all such legislative and procedural efforts. Every time he allows the environment to be diminished, he must be challenged. Every time he proposes policies that hurt the poor, the working class and the middle class, he must be opposed.

We must also hold accountable all who are in Congress and in the administrative branch when they attempt to overturn policies that hurt Americans and to establish policies that disadvantage whole groups of Americans.

You can call it the resistance. You can call it the opposition. You can call it standing up for the rights and responsibilities of all Americans. But act we must.