He delayed publication for years (in the proverbial desk drawer) while he attempted to develop a positive and politically acceptable spin on the results (self censorship). He is also probably one of the top ten most prestiguous living social scientists. Consider the incentives of researchers with less accumulated social capital who are far easier to attack for their findings.

Holding on to publishing the results because you don't like the political consequences sounds like self-censorship to me

It's "self-censorship" no more than I am self-censoring myself right now, in this comment.

Reinvigorating your old work for publication, once you have a commercially viable avenue to promote it, is pretty average capitalism.

Plenty of work that is politically awkward is published under a strict pseudonym. This wasn't - and the author's position is that it was their choice not to publish.