What Rand did have going for her in my opinion is a truly wicked ability to spot the falsehoods in many of the liberal nostrums of the day and in ours as well, and to place them in the mouths of her villains in words that are unerringly accurate. That may explain the heat on the part of the Slate authors. Somebody's ox got gored. That's just a guess but I'd bet it's a good one.
But as far as Rand being in any way the ideological root of the Tea Party movement, I just don't see it. There really isn't anything much Objectivist about that movement, no Aristotle, no bleatings about money being a measure of virtue instead of merely a medium. Not Objectivist at all as I understand the term. There's a great deal of rebellion against the stifling hand of political correctness, as there is in Rand's characters as well, but that's an awfully peripheral relationship. The roots bear little resemblance. IMHO, of course.
I think there is some commonality between Rand's views of the endgame of liberalism and what we are seeing now, just as some business owners talk about going Galt if the Dem agenda passes. But otherwise there is little in the way of shared beliefs between Objectivism and the Tea Party movement. But to a liberal, all us right-wing nutcases look the same.