I think some of the problem is just adjustment into a new medium. Those of us who have been net-savvy for a while know how to read reviews - I am pretty confident we can all tell an irrational impossible-to-please customer from their bad review, as opposed to a rational customer who genuinely had a poor experience. The problem is that some of these business owners are worried that a poor review from a crazy person will sink them - but I doubt that is the case, if they respond in a calm, rational manner.
I encourage people to read through to the later example of the salon owner. Even if the owner had not caused the unhappy customer to up their review rating, I think I, as a potential customer, would have been capable of not placing much weight on 1 bad review out of 30 good ones.