It's matters... when you say "never mind" on my behalf

I admit... my English language is just average, which I would use the simplest possible words to express myself. 

To me, "never mind" is one way to marginalise some matters... it goes lowering the status of a matter to "unimportant" or to trivialise it. 

It is perfectly fine if it is a matter that comes from me and I decided that it should be played down or no longer important at that point of time. And obviously, only I would know how important it weighs right from the start. When the time is unsuitable, I would say, "Never mind, we can talk about the matter again another day or another time." It is not urgent or basically, it could be dealt with later with little impact (when we stretch the timeline). 

However, I personally feel that it matters a lot if we were to label something that someone wants to say as "never mind", even before it was articulated. To say "never mind" even before one says another thing, we are simply marginalising or trivialising what one intends to say, i.e. "what you are going to say is "unimportant"." 

Never go into the mode, and assuming one knows all... It is definitely a lack of basic respect, regardless how experience or senior we think we are....