I don't believe this is reflective of a dislike of disagreement. A debate doesn't have to be ill-mannered nor the debaters disrespectful.
Disagreeing with someone's position on an issue requires that you listen to that person's position and formulate a response that successfully counters it.
Most of us just don't want to spend the time or energy (a) examining our position to the point that we can comfortably defend it, or (b) don't want to concentrate for very long listening to a position with which we disagree, or (c) either.
When I am on a cable chat show I know the entire segment will last about 4 minutes - give or take 30 seconds. If there are two of us plus the studio host that means I will get something on the order of a minute and a half, maybe one minute and 45 seconds, to make my case.
I don't have the time to counter my opponent's argument, all I have time to do is to make my own case, so I go into the studio with the points I want to make. I can talk about anything for a minute 45 - particle physics or quantum theory included; not against a physicist, but I can hold my own against another political hack.
We have all been reduced to communicating exclusively in Twitter feeds, Facebook updates, and talking points.
And, don't send me an email saying you disagree.
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