REP. ILEANA ROS-LEHTINEN, a Florida Republican, is no bomb-thrower or name- ­caller. But when President Trump this week said immigrants would “infest” the United States, she called the comment “repugnant, reprehensible and repulsive.”

We also try not to toss insults around. We believe in civil discourse and in trying to understand the other side’s point of view. But when it comes to tearing children away from their parents at the southern border, there is only one legitimate side. Mr. Trump’s policy for the past weeks has been repugnant, reprehensible and repulsive. It could be justified only by those who view Salvadorans and Hondurans not as humans who deserve to live but as animals — as pests — who “infest.”

We don’t casually use the word “lie,” either. But Mr. Trump and his secretary of homeland security, Kirstjen Nielsen, have been lying about the crisis at the border. It began April 6, when Attorney General Jeff Sessions declared an immediate “zero-tolerance” policy for everyone crossing illegally from Mexico. At any moment, Mr. Trump had it within his power to reverse that policy. Yet the administration maintained that it was powerless, that Democrats were at fault and that only an act of Congress could keep families together.

Now, faced with so much public opposition that Republicans were fearing for their midterm election prospects, Mr. Trump has taken all that back. On Wednesday he signed an executive order that he says will ensure families remain unified. If this does not just become another way of stockpiling migrants, and if the administration implements the order competently and humanely — which certainly cannot be assumed — it will be an improvement.

But all the damage can’t be undone, and certainly all the lessons shouldn’t be unlearned. The zero-tolerance policy was implemented so chaotically, with so little forethought — with about as much care as you would expend on infesting animals — that one former U.S. immigration chief warned that some parents may never find their children again. Even for those who are reunited — and children were being torn away at a rate of some 400 per week — the trauma will cause lasting harm to some. Nor will the injury to America’s reputation abroad be easily repaired.

As to lessons, if this episode of barbarism really is coming to an end, we should take heart that the American people rallied to the side of civilization, and that they could still make their voice heard through Congress. Reporters did the job they are meant to do, dispatching stories in audio, video, photo and written form, and Americans understood that — whatever the complexities of immigration law and immigration reform — this was wrong. Some officials and politicians understood that, too, and some did not. It will be important to remember which was which.

And it’s important to note that even now, as he promised on Wednesday to reverse his policy of breaking families apart, Mr. Trump and his administration continued to trade in larger untruths about immigration to dehumanize and spread fear. In fact, immigration rates are not soaring. In fact, dangerous criminals are not streaming in from the Middle East. In fact, immigrants — legal and illegal — commit crime at a lower rate than native-born Americans. In fact, most immigrants are doing what they have always done: helping to build up America and secure a better life for their children.

A more honorable president would respect their hard work and humanity.