It's much more analogous to completely razing an entire forest to prevent wood beetles from destroying the trees.
Eventually, somewhere down the line there will probably be healthy trees in this place again, but not for a long time, and the "cure" was a lot more damaging than the initial disease.
Because, you know, cancer's usually not as bad as chemo. And massive k-t level extinction events are much, much worse than anything people do, or will do (with the notable exception of Char)