Note: The following is going to come off as 'harsh' and 'uncaring' to some people. Reader discretion advised.
As pointed out by Waven, yes, there is always a human being behind the screen. Not all of them are 'nice'. Not all of them are helpful. Not all of them are bleeding-heart emotionalists. Some will mean well, but come off as harsh or cold because they are not prolific writers. Some will have a sarcastic personality. Some will be blunt.
Yes, there are human beings behind every screen. Human beings with a vast array of personalities. There will be those that are harsher than others, and that will never change. It does not matter if you are on a forum, in IRC, or walking around in real life.
I have been accused of being 'harsh' or mean before just because I told someone something they needed to hear. Looking back, I do not feel "ashamed" in the least, and take offense at being told that 'we' should all be.
Honestly, this thread made me laugh a few times in a generally amused way. It reminded me of a stranger standing up on a soapbox in the middle of a crowd and shouting "We all need to be nicer to each other!" The nice people will agree, and continue to be nice. The friendy but sarcastic people will make comments to each other. The mean people will continue to be mean. In the end, you have someone standing on a soapbox with only a few people stopping to even pay attention.
That, my friends, is human nature. You can be sad about it, or you can deal with it. It is not about to change.