The Democrats would have begrudgingly unified behind Sanders, especially with Donald Trump as the alternative. His threat from the Clinton wing of the party was never the fact that they wouldn't support him in the General Election, it was the fact that they would have undermined him once in the White House. That is why you make a clear example of someone like DWS, to send a message to other Clintonites that if you step out of line, Sanders would mount your head on a wall as a trophy.
This is something I could never stand. Sanders constantly throws around the word Revolution, but it is the most milk-toast Revolution I have ever seen in my life. Revolutions are not civilized affairs, where people meekly discuss their differences. They are, by definition, an attempt to overthrow a ruling establishment. If successful, the old guard either falls in line or they get purged. This was the only way a Sanders Revolution, if successful, could have ended. Yet, it was clear to me from the moment he dropped the ball with DWS that he didn't have what it took to actually lead the liberal Revolution and take over of the Democratic Party. Therefore, had he been successful and become President, he ran the risk of setting back the broader movement.
One would have thought that Sanders, having lived through the 1960's, would at least be familiar with the work of Alinsky.