As for eradicating diseases by selecting embyros that don't have them... well, I'm afraid first of all that that approach will never truly eradicate a disease unless we get so anally attentive toward it that we choose embryos that don't even carry a single copy of a deleterious mutation. Given that such a thing would have to be done to every conceived embryo, the cost would be enormous and extremely difficult, not to mention ethically unsound (destroying embryos that simply carry a disease gene, even though they don't have the gene, is unethical in my book).
My point on eradicating genetic diseases was more about stopping carriers having children at all rather than discarding embryos. And before anyone goes off on one, that's not a view I subscribe to, but it's the logical extrapolation from some of your arguments. Basically, if someone carries genes for a disease, if they don't breed, they don't pass on those genes, but I believe that (most) people have a right to have children and that children have a right to life, however short it may be.