Those sorts of hypothetical "facts" don't just happen though. At best there might be some research indicating a very high correlation between hair colour and le

Those sorts of hypothetical "facts" don't just happen though. At best there might be some research indicating a very high correlation between hair colour and level of infectiousness. But just as often as not it turns out not to be the straightforward connection an initial finding might suggest. So there's no reason to withhold publishing of the results of such research, but every reason to ensure that new research is presented in a way that makes it clear that they're new preliminary findings that are likely to be overturned as more research is done and better understanding is achieved. If that still sets the mobs loose then your only option is government intervention to protect the victims. Suppressing knowledge about the real world is not a feasible long (or even medium) term strategy anyway - it's there to be discovered by anyone and everyone.