Whenever I write that Newt was, in fact, a lobbyist, I get lots of responses reading "who cares!?" or something to the same effect.
The reason it matters, though, is not because being a lobbyist is inherently bad. The problem is twofold:
1) Newt says he didn't lobby. He did. That means Newt is not telling the truth. A candidate serially telling untruths is a reason to not like that candidate.
2) Newt didn't simply lobby for businesses. He lobbied for businesses that were trying to profit at the expense of everyone else by increasing the size of government. This was what he did at Freddie Mac, this was what he did expanding Medicare to subsidize his pharmaceutical clients, and this was what he did helping ethanol companies get subsidies.