A hurried research in the Internet gave me these results:
http://www.cuttingedge.org/n1084.html : read in the list of books below in the page, look for "New Thought";
See a comment in this page above:
Originally posted by ALightinDarkness
...the reason why some religious institutions do not like masonry is because it promotes a diversity of religious belief...
Originally posted by Fire_In_The_Minds_of_Men
Freemasonic notions of "God" have been all-inclusive or amorphously defined ... Hence, it is no wonder why Freemasonry has attracted an inordinate amount of heretics...
About being against all spiritual stuff. Depends what you mean exactly when you say spiritual. Any kind of spiritual activity that involves a lot effort and complications, I don't see as necessary.