If someone is angry enough to tell you why they hate your product / service, that's great! here's what to do.
1) listen carefully.
2) no matter what they say, understand that they are right through their own unique perception.
3) understand that whatever they say, others are feeling silently.
4) if they are your ideal customer, as in someone you should care deeply about helping, take their frustrations into consideration. if not, focus your efforts on getting in front of the right people, not people like this.
Remember to love the process,have fun being an entrepreneur,don't take life or your business so serious that you forget to enjoy the little things in life that matter.the best things in life aren't things.