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How the earth worms coexist with toxic protein secreting, soil based Bt bacteria for millions of years?

The Cry 1AC gene of the soil based Bacillus thuringenesis is incorporated in Bt Cotton. It is alleged that Bt crops would eliminate Earth Worms and other soil based micro organisms. How is it possible for the earth worms and other micro organisms to coexist and thrive in the same soil with Bacillus thurungiensis for millions of years? If these Bt are really harmful to the soil organisms, earth worms would have been extinct by now. Have the earth worms developed immunity against Cry 1 AC protein in the passage of time ?

The Bt gene that they have incorporated into the cotton is probably specific for cotton-chewing insects. According to Wiki: "The toxicity of each Bt type is limited to one or two insect orders, and is nontoxic to vertebrates and many beneficial arthropods. The reason is that Bt works by binding to the appropriate receptor on the surface of midgut epithelial cells. Any organism that lacks the appropriate receptors in its gut cannot be affected by Bt".

There probably are varieties of Bt toxin that kill earthworms, but it does not follow that earthworms should be extinct. If the level of toxic Bt bacteria in the soil is not too high (and remember that Bt itself has to compete with many other soil bacteria) some worms will always survive to reproduce.
Most animals are susceptible to some kind of lethal bacteria or viruses, humans for instance are afflicted by hundreds of different diseases, but so far none has made us extinct.