First of all I said "chooses" which would indicate that if you are physically unable to have children you would not be going against nature. It is the choice that is critical.

mentally ill, socially inept, retarded, physically disabled, stupid, etc.

There are mentally ill people who do have children, and it is perfectly fine, and quite natural (I like the movie "I am Sam").

Socially Inept and stupid are subjective terms. After all, who desides if a person is socially inept. I was told I was socially inept in seventh grade, and now I am expecting my third child.

Now what do you mean by physically disabled. Missing an arm shouldn't stop you. In truth, unless the disability makes bearing children impossible it shouldn't stop you.

To deny anyone the right to have children who has the power to procreate is denying the nature of the human race.

Exactly how do you figure who's going against their "nature" and who isn't?

Those who willfully chose not to have children are going against, as well as those who persuade or prevent them from having children. As I said, it is in the choice.