Simply those in certain agencies, and some outside them.
Why do some of the scientists outside those agencies (Or in a few cases, inside? Don't know the particulars...) disagree with the ACC theory?
The first thought that comes to my mind is that they believe they have contrary evidence, or proof the no supporting evidence exists.
That or they believe they have found flaws in the ACC theory.
The question is, are they correct in their belief?
What are your opinions on such scientists?