Bill Masen is a kind of everyman character, certainly not the kind of lantern-jawed superhero we might expect to find in such a scenario. Calm, rational, and utterly logical, he's able to see through all the chaos and work out what needs to be done at every turn.
While so many others are running around in a state of panic, Bill's able to keep a cool head, largely because of his training as a botanist. Bill's scientific background allows him to see the triffids, not simply as giant carnivorous monsters, but as objects of study. For it is only through studying them and their behavior that mankind can be saved from a full-blown apocalypse.
Just as it was science that helped create the triffids in the first place—bio-engineered in a Soviet laboratory—so it will be science that must figure out a way to destroy them. That's why it's important that the rational, analytical values of people like Bill Masen must prevail, even though it was the abuse of such values that brought about this almighty catastrophe in the first place.