Let's avoid the religious debate and assume Evolution is real

The prime drivers of evolution are
1) Random gene mutations
2) Survival of the Fittest/Natural Selection

The issue I see is that humans actively fight against natural selection/survival of the fittest...

We have hospitals where we treat down's syndrome, cancer, epilepsy, and all forms of mental and physical retardation

Without intervention, these "bad genes" would die and leave the gene pool... but, we keep these people alive, to pass on "bad genes" to the next generation

I know it sounds callous, etc., but it seems like a stupid idea to fill the gene pool with "bad genes", rather than let nature take it's course and kill off the poor bastards who drew the short straw

If a dog breeder had a dog with an obvious deformity, it would not use the dog for breeding purposes... that would be stupid to contaminate the breed's gene pool