Old saying does not apply everywhere

When there is a bad egg in the entire basket, does it mean that every eggs will be bad in the basket? I'm certain the answer for all is no, that's for sure. But let's try this again, a chicken in the barn catch a bird flu, does it mean that every chicken have bird flu? This time I am sure it is without a doubt yes for all countries! And what does we, as human did? We eliminate all in the barn. Isn't this contradicting to the saying?

By reading this, I guess if I continue to write after the first paragraph, I will be charged. So i better stop. Haha..