If my reading of patio11's business of software stance is accurate, I believe he'd say these irate emails are actually helpful signals to you that these people

If my reading of patio11's business of software stance is accurate, I believe he'd say these irate emails are actually helpful signals to you that these people are not a market you want to bother serving! Because they have so little invested in understanding your product and making the most of it, they need to compensate with volume and vitriol. It's better to focus on people who more strongly need and want what you are selling and are willing to signal that with $$.