I agree with most everything in your post Lady Lee.
However, I'm not sure what can be done about it as each of has our own personal perceptions which are layered over with a lifetime of personal experiences that have contributed to the biases of our perspectives. The meaning that we perceive in the messages we receive is our own. Sometimes it meshes with the intention of the sender of the message, sometimes it doesn't.
We can attempt to take personal bias out of our discussions and argue solely on the merit of the logic of the statements. Learning the logical fallacies and disciplining ourselves not to use them, and learning the scientific method of analysis which attempts to eliminate personal bias in information collecting can be of great use in this regard. But until someone can figure out a way to weed out human ego from the equation, I don't think we will ever be 100 percent successful in arguing different positions solely on their merit alone.
I've been told I'm argumentative by enough people to concede there must be truth in it. I've examined myself to see what the "hook" is that lures me in every time. In truth, it's not "every time" because there are literally thousands of threads I never comment on. In real life, I tend to always accommodate the other person's preference. Most stuff seems too small to make an issue of to me.
So, I've examined which topics hook me every time and what it is about them that hooks me. I've noticed two over-riding themes for myself. One is "unfairness". If I think a person is being unfairly characterized based upon the known facts, I will get "hooked". If I think an issue is important because it has the potential to be harmful or helpful in some way, and the issue is being skewed in a way that I believe is unbalanced or unfair, then again, I will get hooked.
I realize that "unfair" and "unbalanced" are also meanings I have constructed over the years too and are not some ultimate "truth". The topics that I think are important are also unique to me and arise out of my experiences as does the meaning "important". In my quest to fight for what I think is "important" and "fair", I will often dig in my heels and I'm not always the epitome of kindness and tact. (Hard to believe, I know!)
That being said, I don't believe that arguing is a bad thing. For me arguing is a bit of an intellectual exercise. It is a way to expose all sides of an issue so the best decisions can be made, instead of just going along with the status quo. Many people are very comfortable with the status quo and literally "hate" those who challenge their opinions just because they hate to be moved out of their comfort zone and they hate to be challenged in any way. Those are the people who will usually end up making it personal. For them it is personal. Sometimes their very ego identity is resting on winning the argument and that is powerful survival mechanism when triggered. No one wants to die, including ego.
For them I say, "Too bad!" Everyone needs to learn that their ego can take a hit and they can survive. Everyone needs to examine themselves. Everyone could use a good paradigm shifting now and again, whether they like it or not.
I like what you say about not taking our perceptions of other posters from thread to thread. I try very hard to do this and treat each thread as a fresh subject on its own merits. However, since posters, including myself, tend to take their posting styles, egos, and personal biases with them from thread to thread its really hard for me not to "react" to them in the same manner. You can see the dilemma.
Everyone could try a nice 24 hour cooling period before they submit their posts. I suspect the forum would die a quick death though. Conflict sustains discussion forums. Conflict is essential to a good story, any writer will tell you that. No conflict to resolve, no movie or book. Just everyone going about their own business and minding their own business.
A couple of years ago, a few posters from this forum were invited to take part in a private discussion forum for like minded "thinkers". I was one of them. I greatly admired and respected every other poster who was in the little club. After about a week, we all got bored of agreeing with each other and came back to JWD. We agreed on pretty much everything and had nothing to discuss.