"My objection is not that Casey is a Scientologist, though I think it is legitimate to criticize anyone who knowingly supports the unethical activities of the Church of Scientology. Rather, my objection is to his making unfounded claims based on Scientology and Hubbard doctrines without being open about his sources. It's a common tactic by the Church of Scientology and other cults to use front groups and try to conceal their nature until after they've persuaded someone to participate in a program--the Unification Church calls it "heavenly deception." I've also wondered to what extent Scientology principles are used in Casey's investment advice, and whether Casey has promoted investment in Scientology-related companies, and whether there were any other Scientologists on Browne's financial committee, but I haven't seen any evidence of those things."
I don't know personally, but reader 'RM' sent me this link that has the evidence in question and it's an interesting read. I particularly agree with this section from an author obviously well-read in the whacked-out world of Hubbard:
Also, interesting is the way the normally err......unafraid to opine Casey has apparently had more than one chance to make a simple denial of his possible Scientology links but has remained very quiet about the subject. Go have a look for yourself.