That the First Nations would nickname men for their clothing is hardly surprising. There was an Anglican convent in my Toronto neighbourhood when I was growing up, and as the Anglican sisters wore blue habits, my family called them "The Blue Nuns." Meanwhile, we were known by another family in the parish as "The Hat Family" because my mother and all her daughters wore hats to church. The nickname was faintly derisive, as if there was something unusual and pompous about women wearing hats to church.
Because most of us can see, we describe people primarily by what they look like, including what they wear, especially if they wear a uniform. Because most of us have reason, we make judgments about people based on what they look like: sometimes judgement is faulty, and sometimes it is not. The onus is usually on the wearer not to give a false or offensive impression, but sometimes the person looking at him or her is simply uncharitable or an out-and-out bigot. The kind of person who calls a Catholic priest or bishop "a man in a dress" is obviously an out-and-out bigot, especially if he would refrain from saying the same of a Gulf Arab, a Scottish piper or a Ladyboy of Bangkok.
The soutane is not women's wear: au contraire! The nun's habit, for example, is nothing like a soutane: it doesn't have 33 buttons, and it doesn't have a sash. It doesn't bear the hallmark of men's tailoring, even if it is very well made indeed. There is no more manly garment than a soutane, for only a man can wear it. Indeed, only a man in, or destined for, holy orders can wear it and, happily, few laymen would spend the money on the real thing for a Hallowe'en costume.
(The famous Gammarelli's makes made-to-measure cassocks and clerical suits, and I find their realistic assessment of the variety of priestly figures very amusing.)
Priestly garb is very important for practising Catholics because we are emotionally attached to priests-in-general and often need to know at a glance if a man is a priest. When we need help, or when we go to Mass or confession, we usually don't have time to find out all about Father So-and-so (if we even know his name). We also may need the visual cue of the uniform to remind of us the authority from which he speaks. An authoritative man in blue jeans may seem like a bully, whereas an authoritative man in a cassock or (at least) Roman collar will seem more ... authoritative.
Besides, the priest who looks like a priest may also temper his tone to match his cloth. The chap in the blue jeans may be thinking "Hey, my blue jeans make me look like a cool, relaxed, authentic guy who's keeping it real, so I can say whatever I want"-- the man in the Roman collar may be a little more careful. Meanwhile, the priest in blue jeans does not look like a priest. He looks like a guy. Maybe a nice guy, but maybe not. I remember being "welcomed" to a historic seminary of tremendous architecture and history by its rector, an unhappy hippy-like man in sandals and jeans. "Welcome," he said bombastically but with the least convincing tone I have ever heard, poor chap.
He might have been having a bad day. A priest who sits in a confession room in lay clothes is much more incongruous. I will never forget walking into a confession room and seeing a pop-eyed young man in golf shirt and chinos instead of a priest. For a startled moment, I thought a lunatic had walked in off the street. He was not even wearing a stole. At my Jesuit theologate, when a priest-prof heard my confession, he always put on a stole. "I could put on a stole," said the poor young priest in a golf shirt, but by then my nerves were so shot, I just excused myself and went away.
This is what I learned in Introduction to Ministry 101: Laypeople Are Vulnerable To Priests. This is one important reason why priests should look like priests. Looking like a priest means wearing the uniform of a priest, just as looking like a police officer means wearing the uniform of a police officer. If a uniformed cop showed up at my door without a uniform, I wouldn't let him in. If a plainclothes detective showed up (as they only seem to on TV) with an ID card, I would spend a long time in the doorway asking why a detective, not a uniformed cop, was at my door. Police are there to serve the public, not the public to serve the police. Priests are called to serve the sheep, not the sheep to make the priests feel like they are super-special just for being "Mike" or "Tom" or "Jim." They aren't.
When I went to see a bishop the other day, it wasn't because he was a nice man (although he is) but because he was a bishop. (You could tell he was a priest because he was in black clericals and a bishop because wore a bishop's ring.) Because he was a bishop, I wore a smart suit. Because he was a bishop, I stood up when he came into the room. Because he was a bishop, I would have been shocked if he had come to the important-to-me meeting in blue jeans. Naturally, because he is a good bishop, he didn't.
We are all deeply influenced by externals, which is why God does indeed care about what we wear. (Look what happened to the wedding guest who turned up without a wedding garment.) I feel proud to be seen with a man who is smartly dressed, whether he is a layman or a priest. And on a warm day, I am conscious that anyone can tell at a glance at my necklace that I am a Christian, and so I think a little more about my public behaviour and am more attentive to the cry of the poor. When I see nuns in habit or priests in clerical suits or--even better--cassocks, I am reminded of Christian teachings, particularly about self-denial and service.
Clerical suits came into fashion in Europe because of anti-Catholic, anti-clerical laws, and they are indeed useful in places where Catholic priests are still considered brother-in-law to the devil, e.g. numerous pockets of Scotland. This is another reason why soutanes make me so happy: they suggest that the wearer is a confident and happy priest and that he is perfectly safe.
Given the latest scandal from Rome, I should say something about joy in the uniform. When I was in elementary school, I dreamed of going to my high school. Because the nicest girl in my class had said she was going to go to Loretto Abbey like her--to me, glamourous--teenage cousin, I decided I too would go to Loretto Abbey. I still remember the joy of trying on my uniform in the shop, and that was a long time ago.
I had dreamed for so long of joining the great sorority of Catholic high school girls, and at last I had. It wasn't just BEING a high school girl, of course: it was all that being an Abbey girl entailed: further education, protection from sexual harassment, being regarded as a young lady instead of a kid, great architecture, the traditions of an institution whose Latin motto meant "As I breathe, I believe in the Cross"... All the same, I looked in the mirror and gloried in the first sight of myself wearing the uniform. Perhaps you will laugh at this, but according to one Argentinian strain of thought, women are vain and such things are expected of us.