Josh Marshall should get a comments section. Well, not really, but if he did he'd have more exposure to the ability of those on the right to continue to claim something even after it has been proven to be demonstrably false.
They're just liars. And, no one bothers to hold them accountable, and no one holds them to any standard.
...to be fair, the person in question, Roger Simon, has corrected his post and can thus be taken off the liars list. But, here's a sampling of people who have pushed this idea about Reid supporting social security privatization (not all the links are for such people, but a lot are).
Maybe they're all just honest idiots. Or, maybe they're just taking their orders from Dear Leader Glenn.