At its core NLP is basically little more than a notational system for mental processes which is a pretty hard thing to discredit scientifically.

It's true that that most of the NLP community revolves around cargo culting a few of these processes though (which most likely indeed aren't scientifically valid.)

Saying that that discredits NLP as a whole is roughly equivalent to saying a programming language is inherently bad because a lot of shitty software has been written in it though.