Ask him questions. When asking questions to an other person, they will automatically try to come up with answers themselves, and so come to a better understanding of their own thoughts or beliefs.
I was wondering, how come you are this charismatic?
X could come up with answers like:
I was just born this way.
I wasn't always like this. I try to effortfully listen to people, and adjust my reactions dynamically to their behaviors.
Then you could ask another question like:
So, what allowed you to develop the skills to listen diligently to others, and how do know what are "charismatic" reactions?
X could say:
Putting out effort communicating with people, trial-and-error, and self-reflection.
Then you could follow up:
Okay, so if it is effort then it depends on energy levels, and if it is trial-and-error then it is influenced by having an avoidant or perfectionistic personality. Wouldn't it be harder for some people to develop charisma then?
This allows X to think about different kind of personalities and talents, and how it would be difficult for some people to achieve charisma. I can imagine that person X wasn't always this charismatic, and developed his communication skills through practice, since he's responding in a way that people are making excuses for their flaws.