Instead of just addressing the cause of the negative review so that it gets buried under better ones, let's go and spend a lot of money on a lawyer and make this one review into a PR disaster!
Someone from Chicago recommended Angie's list to me in downstate Illinois. There's not many reviews for contractors in my town. The concept is great, however I had to pay to sign up, and the user experience isn't great. There's probably free contractor review sites out there, but I don't know of them. Seems like this concept would be a good startup opportunity.
who would pay money for angieslist? The whole point of review sites is to see negative reviews, so why would you want to get reviews from a site that only a tiny portion of people are willing to participate in?
I've paid money for Angie's list, because I was more interested in the quality of reviews over the quantity of them. Seeing reviews from people who self-select to be part of a community that cares enough to pay (a little) adds value to me. I've essentially given up reading reviews on Amazon and Yelp, as there's so much noise. Maybe I'm just an elitist snob, but reading semi-literate "this place sux" reviews doesn't help me.
Note: I'm just explaining the motivation. I'm not affiliated with or evangelizing for Angie's List, I'm a former customer who find a few decent referrals that way.
Finding a reliable contractor for homeowners is very difficult. Traditionally, you found them via word of mouth (your neighbor hired a plumber who did a good job; your cousin the carpenter recommended a roof guy; etc)... you don't need a large network to get some useful information, but AngiesList helps you expand that network by providing more reliable reports from real experiences (i.e., not so easily gamed by sock-puppetry on "free" review sites).
Also, finding a contractor is often about avoiding bad vs. discovering the good.