I don’t entirely agree with it. It’s a bit aggressive, a bit crude, to be so direct.
I’m thinking it can sometimes be a proportionate response to how much we have to deal with that is passive aggressive. For instance, the sickening phenomenon that has become so prevalent lately as to acquire a name – cry-bullying. The powerful or privileged making victims of themselves. More specifically, I’m thinking how, every time someone tries to understand some strange anomaly in public life, and this leads to questioning an official narrative of the powerful, the dismissal is ever at the ready: “conspiracy theorist!”
As someone whose job is to be a theorist, I find it hard to see why this is used as a term of disdain: if there is evidently some possible conspiracy, surely it is better to have a theory of what is going on? Theories generate hypotheses that can be tested. That way, knowledge and wisdom lie.
Or should we just take it that conspiring never happens and everything not conforming to what official sources say is all pure coincidence? No matter the odds?
Frankly, I would say, let’s call out these coincidence theorists! Let’s watch them, aghast, as they pronounce – as I suspect they may have plenty of opportunity over the next day or so – about how any manner of strange circumstances are either inexplicable or purely chance.
But in calling them out, let us not dignify their mendacious contortions with the name of theory, which I would reserve for those who take the trouble to investigate conspiracies.
Let’s call it what it is – bullshit!
 Some serious scholars of the derogatory term ‘conspiracy theorist’ show how it was coined for a specific purpose of narrative control. See, for an overview, the recent interview with Mark Crispin Miller of New York University: https://www.rt.com/shows/renegade-inc/388411-conspiracy-theories-chilling-effect/ . But be aware: that’s on the RT channel, which is, of course, a hotbed of conspiracy theorizing, with the R standing for, yes, RUSSIA! So maybe Mark is a conspiracy theorist about conspiracy theorizing…
 I have particularly in mind today the bringing back into public awareness the unexplained death last year of DNC staffer Seth Rich. Stefan Molyneux has put out an informative video about this: https://www.youtube.com/watch?v=ioBiYxZReTo. There are theories about that terrible event which stand to be tested, and, insofar as it is a matter of public concern, I believe it is better for them to be tested than to be ignored or dismissed.
To be clear, my point is that a theory is worth testing and should not simply be dismissed. Dismissive tactics can involve bullshit. This does not mean that any of the hypotheses dismissed should be assumed true; it just means trying to be clear about what we know as opposed to what we are merely instructed to believe. Conspiracy theorists could themselves engage in bullshit if they try to prop up a theory in the face of contrary evidence. This mistake is presented by narrative correctors as the defining feature of conspiracy theorists. I would say it is what separates a bad conspiracy theorist from a more competent one.