There is no question that Chomsky sometimes loses his way on key issues, but tool or not of whatever sort he cannot be accused on not offering a very deep perspective on American and global political history. IMO.
A lot of extremely smart people are also extremely whacked out.
As an example, I would cite the case of William Shockley. There are many others.
Steve Jobs treated his pancreatic cancer with Indian herbs and meditation. He probably lost years of life as a result. No one could convince him to take another approach.