I've read the Libertarian platform however. I've read CATO. I've read tons of self-professed libertarians on message boards.
And, there is one over-arching unifying philosophy that binds them together: A pull yourself up by your own bootstraps philosophy, a belief that the free market is nearly perfect, and that the Federal Goverment should be small enough to drown in a bathtub.
Nobody in the center-left coalition - not Fiengold, not Bernie Sanders, not Barbara Boxer - would support any of that. Or even be modestly associated with it.