Discerning thoughts aren't negative thoughts.
If a person has a checkered past, sometimes it is valid to point this out. For example, I believe it is useful to point out that Sai Baba was a child molestor so some people will be less likely to get involved with his teachings.
I don't believe it is about smear campaigns. Somebody needs to take on the responsibility of exposing false sources of information.
Regarding learning discrimination, becoming involved with a false guru helped me learn discrimination, but this doesn't mean that everybody needs to get involved with a cult in order to learn discrimination. I believe this learning experience is way over done.
Plus, because I questioned the validity of some supposedly untouchable gurus that nobody would question, I had to do so all by myself. It would've been helpful if there was something I could've read that would've helped me discriminate their false concepts, instead I was all on my own.
Afterwards I made contact with my higher self and spirit guidance and they helped me clear up some of the lose ends I had missed. They helped me see through some false viewpoints I hadn't seen through sufficiently enough.
There is also the matter of how there are unfriendly beings who are trying to prevent the spiritual progress of this World. One of the ways they do so is by getting people involved with false teachings that have just enought benefits so that people fail to see the teachings' shortcomings.
Therefore, it isn't simply a matter of what lessons a person needs, it is also a matter of not enabling misleading beings to have so much success with misleading people.
I don't believe in counting our chickens before they hatch and putting the cart before the horse, so I don't mind getting annoyed about some things. If my cliches bother you, please feel free to be annoyed.

Regarding ACIM versus CWG, pages 50-51 of the first book of CWG says:
Whoever: "All attack is a call for help.
Walsch: "I read that in A Course in Miracles.
Whoever: "I put it there."
Walsch: "Boy, You have an answer for everything."
From page 100 of the 3rd volume of CWG:
Walsch" "What are you saying?"
Whoever: "I'm saying what I said through Judith Schucman (the book says Judith rather than Helen) in A Course in Miracles: You teach what you have to learn."
The above words suggest that God had something to do with ACIM. This is kind of odd because despite what some people such as myself believe about ACIM, if you go by the course's own words God doesn't have anything to do with this World. At most, he would have the holy spirit interact with it. The course itself speaks as if it comes from Jesus.