I agree with what you said in your post.
But I think part of it also has to do with people being WAY to sensitive. I try my best to sound nice, constructive and informative without being "bossy" or "rude" but sometimes I can only type so nice before it becomes fake for crying out loud, and even THEN someone is "upset"
I agree that people should re-read their posts and make sure the wording will get your true meaning across the internet correctly, but while that means everyone acting like adults....acting like adults also means realizing everything can't be as you like it, and not being super over sensitive. It is 50/50 on this issue IMHO.