There are some claims (debatable?) that bat coronavirus studies were conducted at the WHCDC lab. There is more information about the laboratory locations and biosafety concerns in this report: https://www.researchgate.net/publication/350887648_3_WUHAN_L... (written by members of the drastic project; I'm not sure how much of this information is substantiated by other sources but at least the maps appear to be reasonably accurate).
It's particularly bad as a thought-terminating cliche because so much of what defines the label is aesthetic: when figures or institutions in the cultural mainstream speculate wildly, the term is never used (guess how many outlets covered Hillary Clinton's description of Tulsi Gabbard & Jill Stein as "Russian assets" as a "conspiracy theory").
Every theory can be considered with the same tools, parametrized by fundamental factors like how far it is from your current model of the world, what the implications are, etc etc. I freely admit that I've never looked into Flat Earth arguments enough to thoroughly debunk them, but a combination of 1) the amount of things I'd need to change in my model of the world for it to be true and 2) the minimal impact on my life if it were mean that I don't really care to look into it. I can apply the exact same process to every other bit of constructed knowledge, without needing to hand off my critical thinking ability to lizard-brain pattern-matching and mood affiliation like "conspiracy theory".