Again, it depends on your definitions of both "libertarian" and "corporatism". It doesn't sound like you see either as I do.
It's not about definitions. It's about what actually happens. Conservatism by definition opposes intrusive government. But what actually happens is that most conservatives embrace intrusive government.
The argument made by Nader in his book Unstoppable is that, as a treaty, the WTO should have been subject to a two-thirds vote as required by the Constitution instead of being fast tracked through congress as a "trade agreement." If Ralph is correct when he writes the WTO "was the largest single surrender of local, state, and national sovereignty in US history", this is one issue where libertarians and progressives might find common ground.
Except that, as I pointed out, Libertarians don't actually care. They're just as much in bed with the pandering as anyone else.
I'm sure you can find many examples of people who call themselves libertarians who fit this description. But the base ideology of libertarianism is diametrically opposed to corporatism, and the libertarians that I know and work with care a great deal.
I find it interesting that Nader seems to be referring to progressives as if they were an independent political party, when the vast majority of progressives are Democrats. It underscores the fact that Nader seems to foolishly think [hope] that there is an independent political will to fight against the inherent corruption in 21st century American politics.
If so, then hope itself is foolish.