It's not necessary to have "thought leaders" to agree. What matters is how influential the person is among certain groups. This fact has been long used in getting "celebrities" endorse stuff to gain more publicity and momentum in several areas - be they product marketing or social causes - while the facts may be that these celebrities have absolutely no qualification or expertise whatsoever about the product or cause, and thus could not really be called "thought leaders".
ChuckMcM was using jargon that is used especially in markets that are closely tied to academia (pharma, etc.) in which the thought leaders are the influential ones. Extending his 'metaphor' to other groups, thought leaders then would be the members of any group that influences how people think. Thus(sadly) it is true that athletes or other celebrities who may not be qualified or expert in a domain can be, ipso facto, thought leaders to a significant group.
P.S.: Downvoted.