Like most have already said, keep them honest. Seeing how 95% of them you say is really positive, it does seem as though you go into it with a positive attitude.
I haven't had a bad review before, never had one less then steller, but I am sure there is going to be a day when I am not on top of my game, I don't 'click' with the gentleman, or I'll get one with a bad attitude and he will post a negative reveiw on me. When this happens, I will be devestated. I will cry, and blame everyone but myself. I will contact the gentleman to find out what the issue may be. I would hope that I would have more class then to say snide and hateful things.
We are dealing with women's feelings here when we talk about a negative review. Women, by nature, are very emotional creatures. Even though you may have done the 'right' thing and you kept it honest because you are the stand-up type of guy, feelings are still going to be hurt. But there is no place for that in a business.
Keep up the great work you are doing with your honest reviews and realize emotional providers are just part of it. As long as you know you are in the right, and that you have built up the reputation with the gentlemen that you're honest, just brush yourself off and move on to the next 'positive' session!