The editorial asserts, "No one disputes that immigrants who commit violent crimes should be detained." In fact, growing numbers of advocates do dispute this.
When citizens are convicted of crimes, they serve their sentences and rejoin society. When immigrants — even legal permanent residents — commit crimes, they serve their sentences and are often then subjected to the double punishment of deportation and detention by Immigration and Customs Enforcement.
If the federal government started rounding up every citizen with an old conviction and locking them up indefinitely on the grounds that their prior offenses render them a threat to public safety, there would (I hope) be a public outcry. Why should it be any different for immigrants?