Earlier quoted context omitted.
PG seems to have a cynical conception of what "politics" is, since he seems to be saying that practising it is anathema to earnestness. I understand what he means if by "politics" he means self-interest and hoodwinking voters. And that may be his experience of politicians, but it doesn't define the field any more than Mulligans define golf. Champion golfers don't take Mulligans, don't kick their ball closer to the ho…
But I kinda feel like your example proves the point, because I've never seen MLK described as a "politician" or "political figure". Politics as most people understand it is the process of deciding who ought to run the government, and King specifically avoided discussing this ( https://kinginstitute.stanford.edu/king-papers/documents/sta... ) because he felt that doing so would undercut his mission of social change.
People use a broader definition of politics all the time. Office politics. Geopolitics. Realpolitik. Identity politics. Political correctness.