Lobbying is like any other organization of man: government, organized religion, corporations, unions, non-profits, etc. Once they get to a certain size, once people are supported solely by the organization and thus put their need for it to exist and grow and flourish above even its stated purpose, it can (and seemingly inevitably does) become corrupt.

Lobbying on Net Neutrality, done by a bunch of technology workers passionate about the issue is fine. Lobbying on Net Neutrality by professional lobbyists (selling their rolodex) and corporate lawyers, who donate, wine/dine, hire nephews, host fundraisers, etc is not.

It's pretty clear which version people are talking about when they complain about lobbying. (Hint: less to do with reddit, more to do with K Street) And professional lobbying is pretty much inherently corrupt.