President Trump lobbed a new threat on Twitter Friday, pledging to punish "The Radical Left" by "placing Illegal Immigrants in Sanctuary Cities only." In related news, the president remains a fan of randomly capitalizing words.

The president's tweet came after a report by the Washington Post on emails that showed White House officials trying to pressure the Department of Homeland Security to release immigrant detainees in sanctuary cities that are home to Trump's political adversaries — like House Speaker Nancy Pelosi.

Setting aside for a moment the fact that immigrant-heavy, immigrant-friendly cities like San Francisco would not see the arrival of some undocumented asylum seekers as a punishment, the Trump White House has apparently been pushing for this idea for the past six months. It was apparently first proposed in November, following the mid-term elections.

San Francisco City Attorney Dennis Herrera issued a statement Friday in response, as the Tribune Wire Service reports, calling Trump "morally bankrupt."

"He wants to use people as political pawns," Herrera said. "It’s reprehensible. Here are the facts: immigrants are actually less likely to commit crimes, sanctuary cities are safer and more productive, and the president’s proposal would waste millions in taxpayer funds. A real leader would be working on a bipartisan immigration solution."

SF District Attorney George Gascon reiterated the fact that immigrants are less likely to commit crimes than citizens, and added, "The fact that such a proposal is being peddled by the leader of the free world is an all-time low for American discourse."

Mayor London Breed also had a few words for the president. Breed said, "Yes, immigration is an important issue and we need legislative reform, but that’s not what this President is talking about. We are proud to be a Sanctuary City, and to continue to put forward proposals to support our immigrant communities."

San Francisco has been a Sanctuary City since the mid-1980s. The policy is intended to create a safer city in which undocumented immigrants feel safe to come forward to report crimes to police without fear of deportation.

As the Washington Post reports, in 34 Sanctuary Cities across the country, the population of immigrants tends to be 6 percent higher, on average, than in non-Sanctuary Cities.