Sunlight also causes cancer, but we're not about to blot out the sun. ZeroHedge's tagline is actually macabrely appropriate here.

Things designed to kill stuff, aren't always dangerous to other stuff. Caffeine, in example, is crazy-dangerous to a lot of life. Cocoa has stuff in it that's toxic to everything but humans and rats (or at least our tolerances to these things are much higher than most other animals). Deadly nightshade propagates by birds eating the berries, they don't get poisoned like mammals do.

But it is a good general rule that if something kills one thing, it just might be dangerous to other things, too. Even if people with direct financial incentive to let it be, say you should let it be, the possibility of a toxin being toxic is just ever so slightly higher than a random other additive. And needs even more scrutiny because of it. Scrutiny and studies NOT performed by the ones with financial incentives.

Leaded gasoline had plenty of defenders and industry plant "scientists" claiming its safety, too.