Because they’re critiquing him from the right for hurting Kamala’s chances. Plus they say this:

Yet fascists are not alone in their mad drive, both here and abroad, to destroy the last vestiges of liberal democracy and replace it with a totalitarian tyranny of unbridled militarism, racism, and imperialism. Among those facilitating this nefarious outcome in the U.S.A. are three presidential candidates smugly professing to be anti-fascist and progressive, even socialist: Jill Stein, M.D, of the Green Party; Claudia de la Cruz, M.A., of the Party for Socialism and Liberation; and Cornel Ronald West, Ph.D, of the newly-hatched Justice for All Party. None has a snowball’s chance in hell of garnering, either individually or collectively, anywhere near 5% of the vote in any state, let alone winning; but each can and will dilute the vote for the only viable anti-MAGA candidate, Kamala Harris

edit: beat to the punch