Look at the present African American office holders; most if not many were activists and radicals. In fact, that's how they got into office in the first place.
As the author pointed out, Indigenous people and Black folks were the first "progressives". They also were the first radicals (Think about it). Our people have a history of radicalism. From Nat Turner to Martin Delany and Frederick Douglass to Lucy Parsons and Hubert Harrison to Kathleen Cleaver, Angela Davis and Assata Shakur and everybody in between who I haven't mentioned.
Both Bernie and Biden represent a style of politics that is obsolete: the 60's radical and the accommodating Democrat. If not for the existential threat posed by the Trump presidency, neither man would be seriously considered as a serious candidate. While both men have made many positive contributions to their causes, the time has come for them to step off stage and let younger and better candidates shine. Of course they would be consulted for their wisdom and experience; something Trump is seriously lacking in any aspect of his life and it shows.
As a Socialist, I will be eternally grateful to Sen. Sanders for bringing Socialism back to the surface and making it possible for Socialists like me to operate in the open. But now is the time for the next stage of development and I fear that this is less of a movement than it is an ego trip disguised as a campaign. If you read the Democratic Platform of 2016, and listen to the discussions of the benefits of M4A, he's already won. To use a biblical reference, Moses had to give way to Aaron in order to lead his people to "The Promised Land". So too should Bernie and Biden.