Have you read much of his writing style, or any of his disputes with others? They seem to always end up in hyperbolic, very personal polemics, like this one. Look up his encounters over the years with Bruce Perens, or RMS several times, or anyone ESR considers a "left-liberal". Also, climate scientists are malevolent frauds, in his view, Barack Obama is the worst president and anyone who can't see that is intellectually dishonest, etc., etc.
Honestly I suspect his distaste for Stallman has more to do with general politics than free-software politics in particular; ESR is an anarcho-capitalist and Stallman is leftish.
Not that that makes ESR particularly unique, but I wouldn't nominate him as a representative of even-keeled pragmatists; his temperament is much closer to the firebrand type that RMS and Theo de Raadt represent.
