Madgran -- In that case, I actually have a different feeling...
IF a child is trying to manipulate their parent(s) with the threat of No Contact and the parent 'gives in', then they are now enabling the bad behavior. If they don't 'give in' and the child 'walks away', then the parent has done the most emotionally healthy thing for ALL involved.
It ends the bad behavior of the AC because they know their 'demands' will not be catered to. It also shows any grand-children that healthy adults do not use threats and intimidation to get what they want and if they do, there will be no "reward".
That's assuming the AC is an abuser/manipulator.
On the alternate side, if it is the parent that is abusive and the AC says, "Until you can start doing 'this' or stop doing 'that' we will have to go No Contact..."
That is the grey area because much of the time abusive parents will claim that the 'demands' like I made before the 'final letter' were "too much" and I was being unreasonable and therefore my cut-off was a threat/manipulation in their eyes.
So maybe some adults are demanding cars, houses, child-minding or whatever and that is just ridiculous and obviously abuse.
My 'demands' of, "Don't raise your voices around me to each other or to Me." or, "If I say 'no'? That is the end of the conversation. If you continue on the same subject after I have said 'no'. I will hang up." and silly things like that were just "too much".