I must confess that I don't seem any substantial disagreement between my articulation of EY's views and pleeppleep's articulation.

There are certain kinds of inter-personal conflicts that effect a person's mental processes such that the person does not update on the evidence the way rationality says they should. These inter-personal conflicts can profitably labelled with the word "politics." But these inter-personal conflicts include more than those I've labeled "partisan electioneering."

Whether "status-challenge" or "threat-to-personal-identity" is the more accurate description of the causal factors leading to this phenomena is not particularly important to understanding what EY meant when he said "Politics is the mindkiller."