Conspiracy or genuine concern?

J

What do you think divides a conspiracy theory and a worthy concern?

Is it a thin line or gorge?

Is someone who is very skeptical of " the Man"/govt/corporation/group, etc always going to be accused of being a conspiracist or does the particular subject matter?

An example could be Govt nutrition guidelines, for years promoting low fat or sugar free diets it was found that the studies used to defend it were inaccurate and had massive conflicts of interest; the govt did know the studies were flimsy at the time.

Some people took this as govt being in bed with sugar industry/big Corp food (Nestle, InBev, etc.) and knowingly promoting unhealthy diets for "population control" or mass Guinea pig studies.

Give other examples if you can please.