The Left expected Anthony Kennedy to not only write and join progressive decisions, but also to chain himself to his chair like a protester until a Democrat won the presidency.

It is easy to understand why conservatives are not sad about Supreme Court Justice Anthony Kennedy’s retirement: “Kennedy did not owe conservatives decisions that they liked[, but] the conscientious application of the law [and] they did not get it.” It is easy to see why progressives are sad: they fear his successor will be worse, from their perspective.

In this context, it might be less easy to see why progressives are dumping on Kennedy as he makes his way to the chamber door. Yet this reaction gets at the heart of progressivism and should be a lesson to all.

The highest-profile complaint comes from Jim Obergefell, the plaintiff in the Supreme Court case legalizing same-sex marriage, in an opinion authored by Kennedy. Writing for Time magazine, Obergefell seems to think Kennedy owed people a duty beyond the oath of his office: “I struggle to understand how Justice Kennedy can look at our current environment and retire, knowing that his legacy of compassion and dignity, not to mention the civil rights of millions of people, are in serious risk.”

He adds: “Before his retirement announcement, as a member of the LGBTQ community, I saw Kennedy as something of a hero,” with the implication that he is not now. That’s some way to thank Kennedy for his service.

In a column at Slate, “Anthony Kennedy Just Destroyed His Legacy as a Gay Rights Hero,” Mark Joseph Stern makes overt what Obergefell implies: if Kennedy wanted to protect his legacy, he had a duty to retire while a Democrat occupied the White House.

At The New Republic, Andrew Cohen begrudgingly acknowledges that Kennedy’s decisions on LGBTQ preferences, abortion, and criminal procedure “did deliver votes on occasion to progressive causes.” But Cohen’s main thrust is that “these liberal ‘victories’ are far overshadowed by all the heavy lifting Kennedy did on behalf of conservative causes over the decades.”

Similarly sour sentiments run through the reactions of a number of prestigious law professors Politico surveyed, including Geoffrey R. Stone, Sanford V. Levinson, Corey Brettschneider, Michael Waldman, Robert Post, Barry Friedman, and John Culhane. This framing says much about how progressives view the Supreme Court’s function, but it is worth focusing on the core attitude behind the framing: ingratitude.

As Jonah Goldberg observes in “Suicide of the West,” conservatism springs largely from gratitude for the achievements of western civilization:

And ingratitude is the destroyer’s form. We teach children that the moral of the Goose that Lays the Golden Egg is the danger of greed. But the real moral of the story is ingratitude. A farmer finds an animal, which promises to make him richer than he ever imagined. But rather than nurture and protect this miracle, he resents it for not doing more. In one version, the farmer demands two golden eggs per day. When the goose politely demurs, he kills it out of a sense of entitlement — the opposite of gratitude.

The progressives’ attitude toward Kennedy is one of ingratitude because their attitude toward the Supreme Court (among many other things) is one of entitlement. Under the progressive vision of judges as politicians in robes, progressives had no entitlement to anything from a Republican appointee like Kennedy. Yet the Left expected Kennedy to not only write and join progressive decisions, but also to chain himself to his chair like a protester until a Democrat won the presidency.

As Ed Whelan, president of the Ethics and Public Policy Center, put it: “it’s a version of the Brezhnev Doctrine. What the Left has wrongly seized, it thinks it’s entitled to keep.” The Left’s ungrateful reaction to Kennedy’s retirement should serve as a lesson to everyone else about progressivism. It should also be a particular lesson to two people.

First, there should be a lesson in this for Kennedy’s successor. Kennedy was often said to have suffered from the “Greenhouse Effect,” a phrase popularized by D.C. Appeals Court Judge Laurence Silberman to describe judges whose decisions seemed motivated by their need for approval from former New York Times legal reporter Linda Greenhouse. Whoever moves into Kennedy’s chambers should be on notice that “growing” like a plant won’t stop him or her from being tossed from the elite hothouse into a snowbank the second that person stops being useful to the Left.

The second lesson should be for Chief Justice John Roberts. Progressives hope, and conservatives fear, that Roberts is “growing” his way into becoming Kennedy’s true heir. As BuzzFeed’s Chris Geidner describes it, Roberts “has etched out a position of conservatism that sometimes values the interests and stability of the Supreme Court and federal government more broadly to a greater degree than political conservatives might wish to see.”

If Roberts truly sees himself as an institutionalist, the reaction to Kennedy’s retirement should be instructive. The factions he wants to avoid upsetting will always be upset and give him no credit for his efforts to assuage them. If Roberts wants to preserve the legitimacy of the Supreme Court, he can do so by conscientiously applying the law—the very thing Kennedy failed to do in some very big cases.