Hi Adrian,
That’s really great you’ve tried to discuss it with them yourself, but have you also tried giving them some outside information and research that they can look at? I think this could really help them to gain some understanding.
For most people our condition must seem extremely odd and sound almost made up. It would be a bit like a friend coming up to you and saying “I’m allergic to the colour blue, please stop wearing jeans”.
You could try giving them links to websites such as this one, or Misophonia International where they can read about the condition in their own time.
I’m not sure which country you’re based in, but the BBC is a very reputable source here in the UK (where I live) and even they have been reporting on the neurological basis for misophonia. You can see an article here:
http://www.bbc.co.uk/news/health-38842561
I’ve also included some articles from this site below, which I hope you mind find useful:
http://allergictosound.com/articles/should-you-tell-friends-and-family-that-you-have-misophonia/
http://allergictosound.com/articles/help-non-misophonia-suffering-partner-deal-with-misophonia/
http://allergictosound.com/articles/where-to-find-the-best-online-misophonia-support-groups/