This argument is facile. There's an obvious and clear difference between a person representing their own interests and a person paid by a corporation specifically to advance its interests.
It's not a difference which is easy to legislate without unintended consequences (people's own interests frequently overlap with those of their employer, and most people with informed opinions on the implications of a policy are in employed in areas not unlinked to that policy).
What is facile is to argue that a law which simply bans corporations from hiring people describing themselves as lobbyists or government relations professionals will have any real world effect, or to pretend that there are no possible downsides from legislation which might prevent organisations like the EFF from existing or ensure that healthcare professionals are unable to make representations about healthcare to politicians.
It would be entirely possible to write campaign finance laws so that organizations like the EFF can only be funded by private donations and not by corporations, if they want to make campaign contributions or run "issue" advertising. I don't really see what unintended consequences you're referring to. The problem with getting corporate money out of politics is that the people getting it wouldn't like that, not that the law would be difficult to craft in a fair way.
