We learned very different lessons from the 2000 election I guess.
Instead of bashing Nader or his voters we should focus on reforming the election system so that people can vote Green or whatever without fear of spoiling the election. Democratic party loyalists never even mention that. I guess it's more fun to bash the base? Or maybe they like being able to hold people hostage and forcing them to vote for Dems so they don't spoil it and throw it to Republicans? They use the threat of the GOP to force left-wingers to vote Dem. Some people don't appreciate being blackmailed like that. Reform the system so it is no longer an issue.
Or Democrats could mitigate the threat of a challenge from the left by taking on some of the Green/Left agenda, which is also a very popular platform with the American people, and it would help to win. That's the point of the OP after all.
If President Obama will say on TV we should repeal the Taft-Hartley Act, stop fracking for natural gas until it is proven safe, and stop TPP negotiations, then I will promise to vote for Dems for the rest of my life.
If you want to talk about who gets money from right-wing interests, don't worry Democrats take plenty of money from big banks, oil companies, mining companies, bomb builders, gun makers, and the like. And it influences their policies.
I asked my sister why she is voting for Jill Stein. She said "I support the Green Party because they support me".
Wrong answer, but I understand where it comes from. Abandon the left wing and some will split. They have no other way of expressing themselves in the political system because the Democratic Party excludes them. I would like to see that change.