why do so many discussions turn contentious?

Most contentious posts involve people with no knowledge or experience posting what they think they know. 
Best joke these days is who thought access to all the world’s knowledge on the internet would make people stupider. 
Legit posters here own high end audio equipment and invest time in listening. 
Then we have the stupid who have never heard high end audio, can’t bother too, and want to tell us what they think they know. 

Pervasive anxiety, insecurity, feelings of dread, helplessness, anger, frustration--any of these conditions that a person is feeling routinely arouses impulsive, at times, self-destructive defenses. Many feeling hopeless withdraw from social interactions and self-medicate. Yet some can vent frustration, giving aggressive rise of intolerance and even devaluation of others. A safe place to do such is online.

Why do so many discussions turn out so contentious? For the same reason worthless sounding equipment get good reviews in magazines. Everyone wants their beliefs affirmed. IME there are several groups of listeners. The 2 primary groups are those looking for accuracy and those who want music to sound good. I'm an accuracy guy, I want to I hear the good the bad, and the ugly. Then there's what I call the Vandersteen listeners. To my ears Vandersteens dumb down the sound so that nothing really is annoying.  So if you want to enjoy the music without detail, Vandersteens get you there. Then there are folks who are hearing impaired. I know a guy with a serious high frequency impairment. He listens to an Asian girl band which makes most people's ears bleed. IMO, that's it, the if it's there I want to hear it, and if it sucks it sucks, then the my hearing is bad, but I want compensation types. The fact is that if you X, you like X, don't worry about other people!

 "A fool is someone who knows the price of everything and the value of nothing".


Oscar Wilde

In our culture, I think that civil discourse is becoming an historical artifact.