Fair enough. He didn't enter his password, it isn't required to use the service. It is only useful for discovering more people via your contacts (and perhaps to spam them as you, that would be bad).
So they implement a feature poorly. Why the hate? The automatic climate control on my Subaru sucks dead gophers through a hose, but I don't translate the fact that Subaru let an crappy design get of an auxiliary feature get into production with "the car sucks, I'm selling it." Especially if my use of it doesn't require a lot of climate management (which it doesn't in California). I might think differently if the car wouldn't start unless the windows were up and the climate control engaged on automatic, that would cause me to sell it.
So I'm confused about the LinkedIn rant a bit.