Well, some of us definitely try to be friendly. But it's never possible to phrase a comment about a question closing/etc in a manner that you can be 100% sure that nobody will take offence to. The SE system isn't like normal forums, and it takes some time getting used to it. Something that's not really a serious issue on SE may be interpreted as one elsewhere (eg closing--on a traditional forum, closing means the death of a question. On SE, it's a temporary state for many posts.). So I wouldn't be too worried if some of my comments rubbed people the wrong way, though I certainly wouldn't like it. And of course I try to tailor my comments so that newbies can understand them better.
Let me share my experience when I joined Phys.SE: I had recently gotten disillusioned with Wikipedia; there had been some pretty brutal meta-discussion on some policies1. Quite a few of the users I'd admired were participating in it, some were being constructive, some...not so constructive. I was disheartened by the whole episode, and I started (subconsciously, I didn't know it at the time) distancing myself from the 'pedia -- meta discussion and writing userscripts was what I mainly did, and seeing that side of meta discussion hit me hard. Of course, it didn't help that I had a lot of other commitments at that time, mainly academics. Nowadays I poke around sometimes2.
Anyway, I had come across physics.SE a few months later after a suggestion on the science reference desk that I ask my question here (I couldn't get any satisfactory answers then). So I did, and after browsing around, I got hooked :) Part of the reason behind this was that the community here (or what I had experienced of it at the time), was pretty helpful and nice. I became quite active here after that.
Now, if the community hadn't been friendly and had instead been rather rude), then I would have not stayed on after my question got answered. Maybe it's because I'm not a physicist. Maybe the Wikipedia issues had made me sensitive. Maybe I am sensitive in general. Either way, I'm pretty sure that I would have been scared off by this.
Now, I'm not saying that I am a valuable member of the community. Nor am I saying that my contributions are any good. I am saying objectively that if, at the time, I got , you would have lost one user, who has gained 5k+ rep with 200+ answers.
From this, I make two conclusions:
Friendliness is a must-have for our site. Lack of civility can scare users off. Not everyone has a thick skin, and more importantly, people without thick skins are prospective contributors as well.
We seem to be a by-and-large friendly lot. Most of the comments I see on flagged/closevoted posts are pretty OK (though they could be better). The improvements we ought to make are to tailor our comments/etc so that new users have little chance to feel offended.
1. I was not a direct participant in these (except maybe a few comments here and there), just a fly on the wall. Quite a few people had gone into semi-retirement because of it. Looking back, I can't even remenber the specific issues--but there was a variety of them, being discussed more or less simultaneously.
2. A year ago (or was it two?) I did participate extensively in the cleanup of the Wikipedia India Education program fiasco, though. I still love Wikipedia--its goal and its community--but I have just moved on to what I feel is a "better" place for me personally to learn and grow. I