Have you ever noticed that political posters tend to refutations of posts that were not made. For example: a post like 'Leftists always say X, but let me show you why its really Y', when in fact no one had argued X prior to that post?
The reason is the influx of ideas into the mind favours ideas of contention and anger, because in nature such ideas have kept humans from rotting in situations dangerous to them. Anger is a visceral sensation and anger-inducing ideas take first place in the mind's hierarchy of what to consider.
Politics is a great thing to anger people over, and that is why the daily mail and express always go on about 'FURY' and 'DESTROYED', whilst the guardian and independent go for hyperbolic articles 'Theresa may ends everything good for ever, to scratch her friends back'.
The thing is that usually the opposition is not that anger inducing. if i listen to a corbyn speech as a rorke, i may disagree, but if i listen to the entire speech and hear it all in context, i probably won't get as angry if i just listen to soundbites of it. and so that is what the politically-minded (non-centrist) seeks, sound bites that they can get angry at. in fact they do not even need to have an actual quote, if someone else tells them second hand that the opposite side was saying something they disagree with it works far more efficiently.
And thus, for sake of feeding the anger in the mind (just as the wanker feeds his urge to masturbate or the fatty feeds his urge to eat), the poltically minded constantly contemplates what his opposition might be thinking or arguing, not in its entirety, but just enough to make them angry.
Its a sorrowful addiction of sorts.