Luigi Mangione’s federal guilty plea, surely to be followed by another in state court, spares his victim’s family the spectacle of a trial, but in reality no one ever much doubted that he did it — especially not his depraved fans.

Luigi Mangione, 28, pleads guilty to federal stalking charges in Manhattan federal court on Friday. Mangione admitted to the killing of UnitedHealthcare CEO Brian Thompson, reading from a written letter as the slain executive’s widow cried silently in the courtroom gallery. Jane Rosenberg/ Reuters

His lawyer’s talk of the murder as a “tragic event” and the killer as a victim of “the system” barely skirts the surface of the vile delusions required to defend his actions: Meticulously plotting and executing the murder of an innocent man.

The killer’s justification (in his eyes, and his admirers’) only makes the crime more repugnant.

---

Follow The Post’s live updates on Luigi Mangione’s guilty plea in UnitedHealthcare CEO shooting

---

First, because assassination is also an attack on our free society, and on its ample mechanisms for addressing gripes like Mangione’s.

Second, because even if his pathetic excuse for a critique of “the system” made the least bit of sense, killing Brian Thompson was never going to change a damn thing beyond robbing his family of this husband and father.

For the record, running a major health-insurance company is admirable work, playing an important role in how our society —- our democratically elected government — has decided to distribute limited resources in the medical sphere.

Is the system flawed? God, yes — but it beats most of the alternatives.

---

Here’s the latest on accused CEO killer Luigi Mangione’s murder trial

• Read Luigi Mangione’s full speech to the court as he pled guilty to killing of UnitedHealthcare CEO
• Mangione’s twisted fans unapologetically still support him after guilty plea: ‘Revolutionary act of protest’
• Widow of slain United HealthCare boss Brian Thompson makes first public appearance in Manhattan
• Luigi Mangione reveals the twisted way he tricked victim’s company into helping plot sick murder scheme

---

Lots of folks have far deeper gripes with socialized-medicine systems, for example — however little it occurs to the Luigites to learn what other people think, and why.

And improving the system isn’t remotely a matter of identifying the bad guys and making them stop doing their bad things; that approach is no more mature than holding your breath until you get your way.

If Mangione is to receive any mercy, he should admit his vile errors — and name them publicly, in hopes of helping his fans grow behind their juvenile foolishness.

Yet he seemingly decided against an insanity plea because he didn’t want to admit his actions were crazy, so we fear he’s unlikely to admit they were morally perverse, either.

If he is nuts, he might merit our pity; if not, then Luigi Mangione deserves only contempt.

He wasted his own life with this twisted killing, and anyone idolizing him is twisted, too.