David Marcus:

The Left generally argues that part of free speech is exercising it to marginalize the incorrect speech of others. It is a kind of natural selection in which aggressively opposing certain viewpoints is used to banish those viewpoints from responsible mainstream discourse.

It’s an interesting article, but I would suggest a better metaphor here is intellectual eugenics. Like their original progressive forefathers, natural selection is far too slow and inefficient for them, and besides, there’s always the chance you might lose a fair contest. Better to have them, as self-appointed experts, decide which thought-criminals need to have their careers compulsorily sterilized to prevent them from inseminating unwary readers or listeners with their atavistic ideas. The dream of purifying the body politic of moral degeneracy never went away; it just morphed from a fixation on biology to one on ideology. Seizing the means of intellectual reproduction, you might say.