This is NOT an article about another crazy false teacher; instead, this is a more subtle topic. Please read and consider this excellent and thoughtful article from Bob Dewaay at Critical Issues Commentary:
For more clarity on the issue of Pietism:
Here is another article by Bob DeWaay called: How Pietism Deceives Christians
Here is a video explaining the origins of Pietism by Ryan Reeves: Lutheran Pietism
Here is a great lecture by Rod Rosenbladt against Pietism on Issues, Etc.
Here's a short article from Pastor Matt Richard: Keswick Theology: The Exhaustion of Trying to Yield More, Surrender More, And Let Go-Let God