Logical Socialists

The idea of a perfect world sounds so appealing. But let's be realistic here, it's not going to happen. As nice as wishful thinking is, socialists need to take into account the facts. They can disregard them all they want, but they're there. I fail to understand how, not only socialists, but several types of people can formulate these beliefs when they go against so many hard facts. These people can't back up their beliefs, nor can they reach their goals. 

Socialists and Biological Interference

As I was typing up my Q&A on the topic of Socialists View on Human Nature, I found myself using a lot of biological facts to argue against socialists and their goals of becoming "perfect." Apparently, in order for there to be perfect people, there needs to be a perfect environment. Now, I don't know the socialistic definition for perfect, but going off my general meaning, flawless, then there are several issues that run into this process of creating perfect people.
Let's say we have a heritable gene that codes for disease X. In order for a person to have this gene, they must have 2 dominant forms of the allele in the genome, XX. If carries of this gene, Xx, and those who have the disease, were to die out completely without producing offspring first, then eventually the disease will be nonexistent. So why not do this for all diseases like so and bam, there'd be our perfect world? Well an extremely large proportion of the human population would be wiped out. And also, many diseases or disabilities can arise from genetic mutation. Random genetic mutation that is. Due to random assortment of nitrogenous bases, our A's, C's, T's and G's, some unfortunate people suffer from disabilities such as Down Syndrome, caused by an extra gene on chromosome 21.
So, there could never be a "perfect" human population. There will always be genetic mutations.