The term ‘conspiracy theory’ existed long before the CIA used it, but that’s irrelevant.
It has a clear meaning as used across culture, and there will always be SOME term to refer to that meaning.
Namely, “conspiracy theory” refers to a hypothesis deeply violating Occam’s Razor, usually in the context of hypotheses concerning societal events.
Now, if your opposition is calling you a “conspiracy theorist” and you believe they are mistaken, then argue why it’s a mistake.
Do NOT respond by making claims about the term’s origins.
After all, when your opposition vilifies you by falsely labeling you ‘racist’, do you retort that the CIA invented the term (or some claim about its origins)?
No! You argue back, saying why their charge is a baseless slur.
Meanings don’t go away just because you don’t like the current term used to refer to that meaning.
(And, no, it’s not like the ‘n’ word either.)
When someone claims something is a "conspiracy theory" I can almost always say, "That's not a theory, that's a fact!"
And ask, "Would you like me to send you hundreds/thousands of pages of documentation/evidence?"
Sometimes I can add, "Would you like to read about their (i.e., the malignant narcissistic, detrimentally manipulative, murderous psychopaths) conspiracies/plans in their books and/or emails?"
So far, the answer has ALWAYS been "No"/"NO!" 🙄