Ronson's argument is essentially a reactionary liberalism taking shelter in the privilege of the status quo: while the ideals of twitter shaming campaigns are well founded, their application, in practice, is problematic.
That's not how I read the piece at all. I read it as a warning against the ethos of internet shaming, generally, that it's a bad idea, in principle, since none of us can know the context in which an inadvisable post was made. His focus on Sacco was, to me, just an example that was illustrative because of how prominent and public it became. I found it to be a call to dig deeper before passing judgement.
We've all read a viral story then commented on it like we're experts in some field we've not even heard of until our morning coffee. I got the impression Ronson was trying to argue against that sort of instantaneous judgement, generally, and that twitter and facebook shaming happen to be the places where it's most accessible and most destructive to particular individuals.