He's pointing that calling someone a conspiracy theorist is an example of an ad hominem attack. Which it is and was and always will be. Calling someone a conspiracy theorist is talking about a person, not the ideas they are expressing.
According to Paul Graham in his article How to Disagree an ad hominem attack is the second weakest form of disagreement, only a little better than calling someone mean names.
However, in the case of calling someone a conspiracy theorist, I would argue that it actually is an example of name calling as well. It is a negatively charged word. Name calling, according to Paul Graham, is the weakest form of disagreement.
From a logical fundamentals perspective, calling someone a conspiracy theorist has never held water. It can't hold water, unless talking about the character of a person, because it tries to attack the character of a person, rather than refuting their ideas.
Wikipedia, citing conspiracy theory as an example of ad hominem:
https://en.wikipedia.org/wiki/Ad_hominem
It is an error of logic to support that the fact that an ad hominem attack doesn't hold weight means that a thing is right or wrong. The entire point of understanding fallacy is to realize that there is a disconnection between ground truth and any claims reached via their use.
In this particular case, people are talking about Elon being a conspiracy theorist, because he suspects there might be outside actors involved on the basis of known data exportation, known sabotage, and profit motives. These are examples of things tied directly to the question of whether Tesla is experiencing corporate espionage.