This is all going to come back to startups (actually it will come back to getting feedback for any creative endeavour), but first watch this:
Just like you can’t tell an anti-joke if you aren’t willing to endure a few minutes of the audience thinking you’re un-funny, you can’t learn anything useful from talking to people about your business if you aren’t willing to spend a few minutes letting them think your idea is dumb.
After you introduce your idea, they’re going to begin a sentence with something like “So it’s similar to…” or “I like it but…” It’s tempting (and common) to interrupt and “fix” their understanding about how it’s totally different than that competitor or it actually does do the thing they want.
Alternately, they’ll ask a question you have a really good answer to. For example, they’ll start to ramble on about how important security is, and you’ll want to cut in by flipping to your appendix and telling them all about how they have nothing to worry about. This is also a mistake.
In both cases, the listener was about to give you a privileged glimpse into their mental model of the world. Losing that learning is a shame. Unless you’re physically on-stage, pitches are just an introduction, meant to create the context for a conversation and learning.
Watching the joke, you can see Norm adjust based on what is resonating with the audience (you know, like moth names). You can’t figure out what matters and course-correct if you rush through your pitch as a monologue.
Sales literature talks about how you want to establish rapport, understand the customer’s needs, and then sell them a solution in terms of those needs. Developing customer understanding and creating earlyvangelists uses a the same process. Cutting someone off mid-question isn’t going to help you get there, no matter how right you are. Let them think your business is flawed and listen to them tell you why. You’ll learn a lot and have plenty of time to correct them later.
 As founders, we cringe at the thought of being “just like” another product. But in the eyes of the customer, that’s often not a bad thing. If you cut them off, you’ll never know whether they meant it in a positive or negative light, or which specific similarities & differences are meaningful to them.
 In some situations, you won’t have a chance to correct mis-understandings. For example, in a time constrained, on-stage Q&A you need to be more aggressive. In that situation it’s usually okay to burn bridges with the person asking the question in exchange for gains with the rest of the audience.