I don't think you can fix it, it's just the nature of the Internet. I was talking to some older coworkers who were adults before the Internet became mainstream, and they said that before the Internet, your social circle was neighbors and co-workers, so being an ass would have direct, and sometimes physically painful, ramifications. They said that on the Internet, there's no real ramifications for being a horrible person, and you'll always find a group of people that agree with what you say, whereas before you'd get ostracized, or worse, for treating your neighbors/co-workers poorly. I think the best you can do is encourage people to interact outside of the Internet, and hope that the manners required to function IRL stick with them when they go online.
It's not just that, it's the fact that most interaction on the net is text based so you miss out on tone and body language. I feel like some discussions escalate too high on the net due to the text based format.
Definitely. I remember one time a manager from another group at work asked me a question about when a project would be done, and I responded along the lines of "I'm working on it, and I don't know when it'll be done." because it was the truth, and there was nothing else to say about it. They interpreted my single sentence reply as rude and dismissive, then complained to my manager about it. When my manager talked to me about it, he said something like "Oh, ok, your reply is fine, dont worry about it."