Romney's response to Trump's white supremacist comments is essential reading.

"This is a defining moment for President Trump. But much more than that, it is a moment that will define America in the hearts of our children."

Mitt Romney and President Donald Trump have always had a somewhat peculiar relationship.

When Romney ran for president in 2012, Trump alternated between insulting the former Massachusetts governor and ultimately offering his endorsement. Similarly, when Trump campaigned in 2016, Romney slammed Trump's policies and unwillingness to release his tax returns, but cozied up to him after the election.

"Frenemies" is probably the most accurate way to describe their relationship.

Trump and Romney met for dinner in November 2016. The awkward look sums up the relationship pretty well. Photo by Drew Angerer/Getty Images.

After managing to (mostly) bite his tongue over Trump's tumultuous first months in office, Romney laid into him with a fiery Facebook post.

At issue was Trump's moral character and the signal he sent to white supremacists and neo-Nazis in the wake of the Charlottesville protests.

I will dispense for now from discussion of the moral character of the president's Charlottesville statements. Whether he...

Posted by Mitt Romney on Friday, August 18, 2017

There are some key takeaways from Romney's post.

1. "Whether he intended to or not, what he communicated caused racists to rejoice, minorities to weep, and the vast heart of America to mourn."

Getting right to the heart of the matter, Romney directly called out Trump on the message sent to the white supremacist community. Groups picked up on Trump's dog-whistle signals and reacted accordingly.

"His apologists strain to explain that he didn't mean what we heard. But what we heard is now the reality, and unless it is addressed by the president as such, with unprecedented candor and strength, there may commence an unraveling of our national fabric."

Trump during his now-infamous press conference on Aug. 15. Photo by Drew Angerer/Getty Images.

2. "The leaders of our branches of military service have spoken immediately and forcefully, repudiating the implications of the president's words."

It's not every day military leadership is forced to clarify or rebuke something said by the commander in chief, but that's where things stand today. While many of their comments were framed as being simply about having zero tolerance for racism, it's pretty clear who they were referencing.

"[T]he morale and commitment of our forces — made up and sustained by men and women of all races — could be in the balance. Our allies around the world are stunned and our enemies celebrate; America's ability to help secure a peaceful and prosperous world is diminished."

A makeshift memorial to Heather Heyer, who died after being struck by a car driven by an alleged white supremacist on Aug. 12, 2017. Photo by Chip Somodevilla/Getty Images.

3. "In homes across the nation, children are asking their parents what this means."

The president is supposed to be someone we can all look up to, who we can count on to represent all Americans. Trump's first 200 days in office show that his loyalties lie with his core base of supporters and no one else. Romney's point touches on the fact that the divisiveness being forged by Trump's statements could do lasting harm to the country.

"Jews, blacks, Hispanics, Muslims are as much a part of America as whites and Protestants. But today they wonder. Where might this lead? To bitterness and tears, or perhaps to anger and violence?"

White nationalist Richard Spencer is escorted by police out of the Aug. 12, 2017, rally in Charlottesville, Virginia. Photo by Chip Somodevilla/Getty Images.

4. "He should address the American people, acknowledge that he was wrong, apologize."

If there's one thing Trump doesn't do well, it's apologize. In fact, he views apologies as a sign of weakness, instead choosing to double- and triple-down on his flubs. Romney is right: Trump should apologize; he won't though.

"[T]here is no conceivable comparison or moral equivalency between the Nazis — who brutally murdered millions of Jews and who hundreds of thousands of Americans gave their lives to defeat — and the counter-protestors who were outraged to see fools parading the Nazi flag, Nazi armband and Nazi salute."

5. "This is a defining moment for President Trump. But much more than that, it is a moment that will define America in the hearts of our children."

It's hard to overstate the importance of this situation. Trump has essentially said there is some equivalency between white supremacists and people who fight against racism. That's more than just despicable, it's dangerous. It's on him to make this right and not just for the sake of his own political career, but for the sake of the country he purports to lead.

"They are watching, our soldiers are watching, the world is watching. Mr. President, act now for the good of the country."

People hold a vigil outside the White House on Aug. 13, 2017. Photo by Zach Gibson/AFP/Getty Images.