As with most "apparently" good safety initiatives, this one also comes with a potential risk.
First of all, this section describes "slowing down", but a driver may have slowed down to a speed he felt was safe. It's now up to the officer to file the charge based on his own judgment of what was safe. It's these "subjective" calls made by the officer that gets folks upset.
If you want drivers to slow down to 20-30kph (in all three lanes), then you run the risk of causing rear-end collisions occurring well in advance of the emergency scene, as traffic backs up, possibly for miles (ie. on the 401).
A wise man once said, "Slower is Safer", but I'm not sure it's just that simple