The starting point of liberal morality is very different to the end point.
The starting point is a generally permissive one. Liberals don't have such a sense that there are acts which are objectively good or bad. In other words, when an individual makes a moral choice, liberals aren't so concerned what that choice is; rather, the moral good is in individuals making autonomous, self-determining choices - choices of their own.
But the end point of liberalism is a highly coercive and intrusive one. So the question is how do you get from the permissive starting point (you can choose to be or do anything) to what is sometimes called the soft tyranny of a liberal social order?
I think there are two ways that this happens. The first is the one that I often discuss at this site. If the moral good is the freedom of the individual to make self-determining choices, then what matters is that impediments be removed to such choices.
But there are many important aspects of self, identity and relationships that are not self-determined but predetermined. So these things, including our sex and our ethnicity, have to be made not to matter in a liberal order. People who think or act as if they do matter will get caught in accusations of sexism or racism - the famous "isms" that are thrown around endlessly in a liberal society.
Already, then, there has been a shift from a permissive "do whatever" or "you yourself get to choose what is right or wrong" to a more aggressive stance about what is allowed to matter morally. And this moral stance is more intrusive than preliberal moral codes because it is set against beliefs, identities and relationships that are basic to human nature and the human experience.
There's a second aspect to all this which I haven't discussed as much previously. Liberalism is distinct amongst modern movements in wanting to develop a system in which each individual will gets to self-determine its own choices.
The idea, in other words, is that rather than will being expressed for everyone through the choices of a leader or a party, it will be expressed equally by every individual.
If you commit to this kind of system, then it will be thought both dangerous and wrong for people to impose the pursuit of their own self-determining choices to the detriment of the choices of others. That will be thought to violate the ideal of an equal expression of choice.
This then leads to further concepts of right and wrong within a liberal order. It becomes "correct" to adopt a moral attitude not only of equality, but of "non-interference" or "non-infringement" (as the aim is that individuals are left within their own orbits to pursue their own individual choices, unimpeded by those of others).
A "good" liberal will therefore focus on moral qualities that show a commitment to "non-interference" or "non-infringement" of others such as respect, tolerance, non-judgementalism, openness, anti-discrimination, inclusion, diversity and acceptance (as well as fostering a general attitude of "equality").
Also, if the aim is non-infringement this will create a moral focus on individual rights, and if we wish to show ourselves to be open and non-judgemental, we will additionally consider prejudice and bigotry to be primary moral failings.
But why, if liberalism arrives in this roundabout way at a moral attitude derived from "non-infringement", do we finish up with a morality which is so often experienced as oppressive, intrusive and demoralising?
There are several reasons that explain why a liberal morality is demoralising. People generally wish to live in a moral community. But liberalism distorts the usual expression of moral belief, first because it is highly permissive in some areas and second because it is silent in others. The cluster of moral qualities that liberalism recognises all relate to non-infringement, whereas the positive qualities of character that were once widely recognised as virtues, such as loyalty or prudence, are no longer vitally present.
Another reason for demoralisation is that a liberal morality is destabilising to the larger communities that people feel connected to. If it is a virtue to be open and non-discriminating, and if there are thought to be no other moral considerations that might act at times as a counterweight, then a community loses a choice to maintain its own distinctive character.
There are also serious ruptures in the normal ties of solidarity within a community. The liberal morality encourages the elite to identify not with the ordinary members of their own community, but with whoever is thought to be most other or most different. After all, if the entire moral structure is based on being open, non-discriminatory and inclusive then the most virtuous person will be the one who identifies least with his own and most with the "other".
And there's another reason for the rupturing of solidarity. The way to lose moral status and standing within a liberal society is if you are thought to have disregarded the liberal moral virtues by imposing your own self-determining choices to the detriment of the choices of others. This will define you as a privileged class and whichever class you are thought to have deprived will be able to make claims against you.
And so liberal politics, in practice, reintroduces the categories it wants not to matter, but as hostile political forces ("identity politics"), based on the assumption that the very existence of these categories relates to a dynamic of oppression and resistance. For social reality to be perceived in this way is not only demoralising to a sense of social solidarity (e.g. with the sexes set against each other), it will also be felt to be oppressive by those who fall into whatever classes are tagged as oppressors.
Finally, it doesn't matter in the long run if the liberal morality has its origins in non-infringement or non-interference. Once certain qualities are defined as morally authoritative, then they will become the standard for the society as a whole. They can then be imposed either by the state or within the culture in a highly intrusive and coercive way.