I was just reading a little monograph about political philosophy on the internets, the way you do, and there came the all-too-familiar moment in which it asserted “and here you see that the professed ideology of my opponents is at best self-deception on their part, for it is revealed that their true motive is pure lust for power”. And I let out a little sigh at this failure of the Ideological Turing Test. It invalidated the piece's whole argument, for me.
It hardly matters what side this piece was arguing. It galls me when I am told that my political ideas are just a mask for my simple desire to exercise power. It galls me no less when people say the same of my political opponents; if we are to understand what is going on, we must credit our opponents with at least a sincere desire for a better society as they conceive it.
Claiming a pure lust for power as the motives of one's opponents is a mark of the unsophisticated. A childish, cartoon view of politics.
So presuming the sincerity of one's political opponents — if not necessarily their honesty or goodwill — is a habit of the politically sophisticated.
What of fascism? Though it rarely takes root, fascism is always with us. Rarely does it profess to be fascism. And one of its defining features is its radical disinterest in policy, its profound insincerity about its ideology, its pure will-to-power.
This makes the sophisticated vulnerable to fascism's deceptions if they do not learn to recognize its scent.