Atrios took a shot at the Greens, and they've responded in his comments thread with everything from "you can't expect Green votes when you insult them" to "the idea that Nader was saying Gore and Bush were identical was a lie".
Folks, those who are saying "we should be nice, or we'll lose the green vote!" are kind of missing the point, which is that the vote is, by definition, lost. Those who choose to vote Green in states that matter aren't going to vote for Democratic candidates who are centrist enough win the election. They'll go for their man Nader.
(Trying to attract them by changing policy will just encourage them to stay the course, in order to have the Dem candidate move more in their direction.)
And, yes, Bush=Gore was a theme of the Greens; trying to deny it is revisionism. There's nothing wrong with that from a partisan point of view: attacking centrists for being centrists is a logical way of getting outlier votes, and worked well enough for the Reform party in Canada. The problem is that just as Dem rhetoric is ticking off Greens now, Green rhetoric was incredibly insulting to Democrats back in 2000. Nobody's forgotten this.
Greens have also seemed to have not realized that trying to "pull" parties in one direction is useless when the political discourse is being pulled in the other direction. The U.S. right realized it long ago, and has been effectively using a "play the fringe vs. moderate" strategy to pull things rightward over the past ten to fifteen years. Greens have the fringe, but that doesn't work without coordination with the Dems, and they can't coordinate with the Dems without losing their relevance. As at least some of them are partisan more than they are ideological, that won't happen.
Finally, to those Greens (and others) who advocate different voting systems- even if it's constitutional (and I have my suspicions), there's no way that a Republican will enact such a thing, and if the Greens are ensuring Republican victories, it's empty rhetoric. It's academic, at least for the foreseeable future, and possibly forever if it'll require a constitutional amendment. Without it, though, the Greens will never own the presidency, and should stop trying. Some seats in Congress, sure, but not the presidency.