How to nicely handle it when someone tells you a very bad idea

When the options are to lie and be nice, or be honest ... I'm never honest.
  1. Help!
  2. I never know what to do when someone tells me an awful idea.
  3. I usually say something benign...
  4. Like "oh really?"
  5. Or just nod with with a fake "oh, I'm totally absorbing this" face.
  6. But is that really benign if I'm passively encouraging someone to do something that is a very bad idea?
  7. I used to wonder how horrendous singers made it onto American Idol.
  8. Where were their friends and family to save them embarrassment?
  9. Maybe their friends were like me.
  10. Nodding with their stupid faces and quietly allowing them to humiliate themselves.
  11. So what SHOULD I do...
  12. ... to tactfully and painlessly (for both parties)...
  13. ... handle these delicate situations without (basically) lying??
  14. Suggest they research idea with someone who knows better than you.
    Suggested by   @MaddyandOwensMom
  15. I say how it's bad, and then I laugh. So I told the truth and spared the embarrassment. They won't be so confident to try it again.
    Suggested by   @Boogie