You wrote: “I would expect a soldier for whom this is disturbing to refuse, and not to ask whether it is permitted or forbidden.” But the only thing that’s disturbing is the concern that there may be a prohibition here (unless there’s some psychological factor that bothers him, in which case how is this different from just ordinary difficulty in the army that one has to overcome?). So why is it proper to refuse before clarifying whether there is any prohibition here at all?

With all due respect,
I have not managed to understand the outcry of the liberal rabbis over mixed battalions, as though they are utterly forbidden.
After all, they are the very ones who permit mixed society from the outset. Under their guidance, male and female campers march together in Bnei Akiva camps for long days, do shared morale activities that include jumping around and wrapping together of boys and girls, where the distance between that and actual dancing approaches zero, sing soulful songs with a boy next to a girl, go together to comedy movies, and gather all night around a bonfire including many social games.
And not only is this completely acceptable in their eyes, they even see this approach as ideal, actively prefer it over separate society, and completely reject the idea that separation is preferable.
And then suddenly, in the army, slight movements caused by a female soldier carrying a stretcher become a time of religious persecution (even if only metaphorically), and walking together on a march is utterly forbidden.
Can someone rescue me from my confusion? Maybe Rabbi Michi is the head of the liberals everywhere?

As for the accessories of it — shared facilities, say in the army in mixed male/female units — they need to define separate times for showers. And in mixed situations, to really separate the accessories of it — what’s so hard about that? And if it’s truly impossible, then bring portable toilets; for the army that’s pennies.
As for the social side of it — sitting together and singing together is a necessity, but dancing together is permitted when there is clear separation!
As for walking together on a march, you can arrange for the women to be in the back — what’s the problem?
What’s the problem with carrying a female soldier on a stretcher? Let women carry her and men carry men. Or men can carry women only from the front of the stretcher — what’s the problem?

I’m not Rabbi Michi, and certainly not the head of the liberals anywhere.
Still, I’ll try to explain, and may it be accepted as truth from the one who said it.
Liberalization, in my humble opinion, argues for openness of thought,
and not for coercion of thought.
Mixed youth movements are a blessed phenomenon, so long as participation is not forced on someone who is disturbed by it religiously, emotionally, or spiritually.
The moment the army imposes mixed companies not because of the army’s real operational needs but as a religious-feminist agenda, and forces its soldiers to join the move even if they are disturbed by it for any reason, there is an element here of crossing boundaries, and of coercion by the feminist religion (which is not bad in itself, so long as it is rational and considerate).
Of course I’m not sure there is room here for hysteria, but there is certainly room for objections — balanced and rational ones.

A.,
True, I am the head of the liberals only in some places and not everywhere, but still I’ll try to jump in at the head of the line.
1. I don’t know who these liberal rabbis are that we’re talking about or what they wrote. I haven’t heard about this whole matter. But if I’m the one standing at their head, one thing I do know: they have good taste. By the way, Rabbi Medan, who was mentioned here, is far from being a liberal rabbi. And he is certainly not under my command (to my regret and to his delight).
2. There are quite a few differences from the youth-movement question. In a mixed youth movement there is some supervision (counselors, male and female coordinators), and the framework is religious. In the army most people are secular, meaning people who generally don’t care about prohibited acts (except because of orders), and engage in this without disturbance and see nothing wrong with it. There is also an age difference, since youth movement is at high-school age. In the army they stand guard together at night in isolation. The framework creates such situations. In a youth movement this could at most be an initiative of the kids themselves. A mixed youth movement has value, because people need to be educated toward values, and without the mixing the participants won’t come. Moreover, there is also value in learning to live in mixed society, because that is what life has in store for them. The prohibitions, if they arise, are a side effect and not a necessary one. But in the army there is no value to mixed service (on the contrary, it probably harms operationally as well). And so on.

To Oren,
What I wrote — that the soldier should refuse — is not necessarily because of a halakhic prohibition, but because he feels that the matter disturbs him spiritually, even if there is no formal halakhic prohibition on it. That alone is enough to refuse. Is that any worse than conscientious refusal by a secular soldier based on his own values? Why should only a halakhic prohibition justify refusal?
Beyond that, the halakhic prohibition of forbidden thoughts and modesty depends on the person (whether such thoughts are aroused in him or not; whether in the circumstances created for him there is prohibited contact or not; and so on). Therefore, in the end, the soldier himself must bear responsibility and refuse.
On the question of who should issue a halakhic ruling in an unfamiliar and unique situation, it is worth seeing this article:

פסיקת הלכה בשואה ומשמעותה לדורות

The original article to which I refer there is this:

מה אקוב לא קבה א-ל, ומה אזעם לא זעם ה’

Perhaps according to the view that military service is a commandment, one could make a claim of religious persecution, since the new mixed units bring about a situation in which army service in these units becomes a commandment that comes through a transgression.

That seems exaggerated to me, since one can always refuse to serve in a mixed unit, and Rabbi Tau wrote this too in the booklet they just put out. But there is some intuitive point here: if we reach a reality of shared restrooms (and this is not comparable to office restrooms) only in order to mix the sexes, one should stand against it as one stands even over a shoelace. For in the end we do not find shared restrooms in any large institution such as a mall, high-tech laboratories, and so on. And where we do find shared restrooms, in bars and clubs, that is for promiscuity, as is well known.

Moderation is preferable, but sometimes it is better to draw a line in order to set a boundary against the inversion of basic decency that may be happening here.