Michael, this is exactly the type of "sabotaging black movements" that this article is talking about. If you're eager to help, that's great! This movement needs white people who are eager to help. That's exactly what this article is saying. This article is also saying that Hal has a personal fear, through experience, that white people will find the first excuse to STOP supporting the movement as soon as they conveniently can. That's what you've just done with this criticism: "Blacks are blowing it." You're counting yourself out of the equation and blaming other people.
If you feel blamed, shamed, or guilt-tripped by this article... it's probably because you're exactly the culprit it's describing. I'm white, trying to be a better ally every day, and every bit of this article rings true to me. If you are actually interested in helping -- "eager to help" as you say you are -- then STICK AROUND!