Andrew is a professional misunderstander. He dotes on typos and loosely worded phrases. He is quite smart enough to discern other people's intentions, but chooses to make the worst possible reading.
Quoting Darwin on genetics is a dishonest tactic, since Darwin lived before genetics was invented. Darwin was aware of two possible implementations of genetic information: discrete and blended. He observed blended traits and therefore believed that is the way the underlying implementation worked. He was wrong.
It remains a fact that genes detrimental to individuals can be preserved because they benefit a population.
I take it you understand the agent behind the "because" in this statement to be natural selection. Does natural selection have any laws of its own by which we might predeict, test, and observe its operation, or does it act arbitraily and thus allow us to ascribe some purpose after we see the results?