I think my problem with your responses on this thread so far has been that you've taken various liberal positions, said "Obviously this a sacredness value, liberals say it's about harm but they are lying", and not justified this.

"Lying" is not the right word, since it suggests conscious deception. The term I have used consistently is rationalization.

In order to demonstrate that liberal sexual values are sacredness rather than harm based, you'd need to point out some specific practice that was harmless but which liberals still violently opposed [...] or harmful but which liberals supported [...]

Arguing against liberal positions on such matters is very difficult because they tend to be backed by a vast arsenal of rationalizations based on purportedly rational considerations of harm or fairness, often coming from prestigious and accredited intellectual institutions where liberals predominate. This is of course in addition to the dense minefield of "boo lights" where an argument, whatever its real merits, will trigger such outrage in a liberal audience that the discourse will be destroyed and the speaker discredited.

So, while I can readily point out concrete examples of the sort you're asking, unfortunately in many of them, crossing the inferential distances would be an uphill battle, or there would be immediate unpleasantness that I'd rather avoid. Therefore I'll limit myself to a few more vague and general points:

• Laissez-faire in sex leads to all kinds of expensive negative-sum signaling and other games. Why not crack down on those, which would lead to a clear improvement by any utilitarian metric?

• If it's OK for the government to ban smoking and other activities harmful for public health, why not extend such treatment to sexual activities that have obvious and drastic public health implications?

• If the alleged vast inequality of wealth is a legitimate complaint against economic laissez-faire, why is it not legitimate to complain about the vast inequality of sexual and romantic opportunities (and of the related social status) under sexual laissez-faire? (The problem is by no means limited to men, of course.)

• Why the automatic hostility towards the idea that under sexual laissez-faire, a huge segment of the population, which lacks sufficient prudence and self-control, will make disastrous and self-destructive choices, so that restrictive traditional sexual norms may amount to a net harm reduction? Especially since liberals make analogous arguments in favor of paternalistic regulation of practically everything else.

There are many other examples too, but these are the best ones I can think of without either running into enormous inferential distances or sounding too provocative. It really seems to me that liberal norms change suddenly and dramatically towards laissez-faire once sexual matters come under consideration, and I don't see how this could be because their regular considerations of harm and fairness just happen to entail laissez-faire in this particular area and nowhere else.

I agree that certain liberal values are based on sacredness (diversity and anti-racism) or purity (environmentalism), although I have yet to hear any good argument that liberals explicitly value authority.

Explicitly, certainly not often. But in many of their observed views and behaviors, I detect strong authority-based intuitions, even though they will invariably be rationalized as something else. The typical way is to present authority as some kind of neutral and objective expertise, even in areas where this makes no sense.

Once Peter Singer says he can't really see any problems with infanticide because it doesn't harm anyone, the hypothesis that he still is secretly trying to uphold sacredness values just as much as everyone else becomes pretty hard to support.

As I said, I'm not an expert on Singer in particular, and I don't deny the possibility that he might be an outlier in this regard. (Although I do remember reading things from him that seemed to me like a clear case of rationalizing fundamentally non-utilitarian liberal positions.) Also, I agree that someone's serious utilitarian bullet-biting on some issues provides some evidence that he is overall less dedicated to the values of sacredness etc. I do think, however, that you underestimate how often such serious bullet-biters can be inconsistent on other issues.