Optimum number of murders is 0.
So we take steps to prevent murder.
This doesn't make the number of murders 0, but we take the steps because we want to reduce murder as much as possible, because we've agreed it's unacceptable.
Substitute "online misinformation postings" for "murders" above.
The point is just because something is difficult to eliminate is not a good reason to give up trying to eliminate it.
