This is going to sound like a Seinfeld bit... But what the heck is up with people that just refuse to listen to you? I have this happen all the time... I've been designing and building my products for over 10 years, and been doing it off and on as a hobby since I was a kid. I often get people that ask me the most crazy questions or have the most crazy ideas... I try to politely dissuade them from following through with their idea, explaining why it won't work... and it's like... in one ear and out the other. It's almost like they purposely distrust me... It's like, they want to do it their way MORE, because I say it won't work. I guess I could understand if I was trying to steer them towards something more expensive. But it's usually the OPPOSITE. They have some nutty idea that will cost a fortune, and I know it's not going to work, so I try to talk them into the right thing, which actually makes me LESS money... and they just won't listen. Then if you just give up and let them buy all the stuff, they get mad when it doesn't work and act like you never told them it wouldn't work.
Then I get the people who don't even want to buy anything, but just randomly email me to tell me why a product can't possibly work... The old armchair expert retired guys, that apparently have nothing better to do. The fact that hundreds of people have bought a product and have no problem with it, doesn't seem to change their opinion that it can't possibly work.
Crazy people out there.