You're mistaken in applying the same standards to personal and deliberative decisions. The decision to enroll in cryonics is different in kind from the decision to promote safe AI for the public good. The first should be based on the belief that cryonics claims are true; the second should be based (ultimately) on the marginal value of advocacy in advancing the discussion. The failure to understand this distinction is a major failing in public rationality. For elaboration, see The distinct functions of belief and opinion.