On Sunday’s Last Week Tonight, ahead of the crucial midterm elections, John Oliver focused on Trump’s brutal family separation policy—how it happened (“incompetently and cruelly”), and why (racism!). The rage-inducing segment is important viewing to understand the details of the policy and how America got there.

While seeking asylum in the US has been legal since World War II as defined by national and international law, the Trump administration has been framing it as a crime, and using that to justify its horrible policies. “Conservative immigration arguments essentially now follow a pretty clear pattern: crossing the border is a crime, therefore anyone crossing it is a criminal, and since all criminals are dangerous, anyone crossing the border is a dangerous criminal,” Oliver summarizes. We know what happened next: the administration used its “zero-tolerance” policy to forcibly separate thousands of children from their parents.

One hundred days have passed since a federal judge ordered the Trump administration to reunite the thousands of children officials snatched from their parents, and as of October, at least 47 were still separated. We don’t know how many are currently separated.

Yet Trump is already again flirting with the idea of bringing back the cruel, inhumane policy—this time, drumming up fear with talks of an “invasion” of asylum seekers in a caravan thousands of miles away from the U.S. border and sending military to the border. “Even though the language of war is being used, there is not a war,” Oliver says. “And the only reason people keep talking like there is one is to give themselves permission to make the choices they want to be forced to make. But family separation cannot be one of them.”

Though the family separation policy is tabled for now, the trauma it wrought is theoretically unending, and must not be ignored. For more, watch the full clip above.