I disagree with you strongly there. There are moments that can hurt but Clinton already had major name recognition in democratic circles that gave her a huge edge. Sanders brought more energy into the campaign but it was always going to be a major uphill climb for him.
Particularly with superdelegates. Many of the states that Sanders won were also cacus states. Which are hardly democratic processes in and of themselves.
I vastly preferred Sanders over Clinton, but at the same time I do not think one moment did him in. He was always fighting uphill and never had support of the general establishment. Clinton still won more primaries and more supderdelegates.
Many primary voters are tuned in, but I doubt that one statement from one candidate is going to do them in at that point. At least it did not seem that way to me.
He did have a point about Hillary taking all of that money from Wall Street and Goldman Sachs and special interest. He definitely could have gotten her there.