Sure, 2-5% of my users are nasty/mean, but let me tell you a little secret: They are immensely frustrated with their life situation and they know how simple the solution should be. If you can show them the light, if you can "flip" these users, they will become your most loyal customers.
I start by telling them, "Hey, every month I get a call like yours where you are so frustrated you want to scream, and let me tell you a secret, if I got a call every day like this... I'd quit this business, but calls like yours are rare and I want to help you through this."
Boom. They're listening, and they're often listening to advice they don't want to hear. What kind of advice? Oh... like, "you will have to work through this and tweak the measurements until it works, because some printer drivers are mysterious and terrible. But once you get it, you'll be rewarded with it working for a long time until you have to buy a new printer."
Still, 50/1000 seems high to me, I like to think I earn the trust of 90% of my nasty/mean customers. Sometimes I'm lucky and I just paste a URL to a FAQ. After 4 years in business I had my first person hang up on me because they kept demanding a simple answer and I would say, "sorry, it's more complicated than that, I don't have a simple answer... I just have two complex answers that contradict each other until you can choose which one is the lesser of two evils."
It could be a book that no one would read: Zen and the Art of Label Printing
A quick video of my app Label LIVE, narrated by yours truly: https://www.youtube.com/watch?v=hnqUP1CZd24