This passage on skillfulness, from Thanissaro Bhikkhu's The Wings to Awakening, provides us, I think, with a helpful way to understand how political decision-making and political action can go wrong.
[T]he definition of skillful states of mind as free of greed, aversion, and delusion, provides a convenient rule of thumb for distinguishing between intentions that are merely good and those that are actually skillful. Sometimes good intentions are colored by ignorance, as when one tries to help another person without knowing the true source of that person’s problem. This would qualify as a good but not a skillful intention. As we have noted, the processes of causality are sensitive and complex. Thus there is no getting by on well-meaning intentions alone. One must monitor one’s actions continually to make sure that they are, in fact, appropriate to the present situation and not based on ignorance. Delusion, even well-meaning delusion, is a source for unskillful acts. For this reason, one needs to be constantly observant of one’s actions and their effects [§6] so that one’s good intentions can truly become skillful, and one’s actions can actually do justice to the specific conditions in the here and now produced by the process of this/that conditionality.
Second, the distinction between skillful and unskillful provides an insightful explanation for the causes for good and evil behavior. This distinction is not limited to the values of any particular society, and it avoids the issue of whether beings are inherently good or bad. When people act in evil ways, it is because they lack skill in the way they think; when they think in skillful ways, they naturally will do good. Because skill is something that can be acquired, the way to goodness is open for all people who want to be good, no matter how badly they have behaved in the past.
When we're thinking about political actions—or any actions, for that matter—a skillful intention is always well-meaning. But not every well-meaning intention is skillful, because the intention or how we carry it out could be clouded by ignorance.
This means we can divide political proposals first into whether they are well-meaning or ill-meaning. But we then need to ask whether those in the former category—which, for most people, is most of them—are skillful in the sense that they are free of ignorance about how well they will play out in the world, and are carried out with a mechanism for learning, as they unfold, if they match our intent and expectations and, if they don't, how to adjust. (Ill-meaning or hateful intentions are definitionally unskillful, no matter how informed the intender is about their consequences. This means a ill-meaning intention that, through ignorance, results in a beneficial effect is, nonetheless, definitionally unskillful.)
The political intentions of someone with a genuinely liberal sensibility are well-meaning. But there are still plenty of political intentions (and policies, and actions) coming from people of genuinely liberal sensibilities that go wrong in that their engagement, and so are unskillful. The person lacks the knowledge to make good policy choices, or they fail to undertake the necessary step of examining the effects of their action to assess whether it in fact reduces suffering.
But illiberal intentions coming from an illiberal sensibility are done with ill-intent. They aren't well-meaning. They aim to cause suffering in the service of illiberal ends. And so they cannot be skillful, even if they achieve their ends.