Poisoning the well is not an insignificant phrase, and derives from historical use of biological vectors to spread disease during siege warfare.

Good point. And the reason the well was chosen was because the attacker knew that the poison would be distributed from there. Similarly, modern disinformation almost certainly focuses its efforts on the most connected communications channels. So by the time the disinformation finds its way to the casual user, it is already too late to prevent it from spreading. I don't think that the source article recognized that point at all.