User: It would be great if your product did FOO.
Me: It does do FOO.
U: No it doesn't.
M: Try pressing the frickimg great button marked FOO.
U: I don't have a FOO button.
M: Send me a screenshot.
M: That's not my product.
U: Yes it is!
M: Look at the screenshots on my product's website. Yours is nothing like that. And mine doesn't even run on your platform.
U: This absolutely is your product and I can't believe how rude you are being.
M: Errrr... WTF? Are you someone I know having a laugh?
U: Right now I am going to write bad things about your product on my blog which has lots of readers.
M: Please do, and don't forget to post the screenshot showing that it's not my product, then maybe some of your many readers will point out your mistake.
(Never heard from again.)