There have been many experiments (most notably the miller experiment) that have proven that organic molecules (among other things) can arise from inorganic molecules, which was considered impossible after pastures discoveries which ushered in the era of vitalism (which was proven false).
And it doesn't matter that humans are nothing more than intelligent animals. We are intelligent. The cause of that is unimportant. We are living beings, with a self identity, and therefore should respect the self identity of others.
And for that matter, moral implications of a fact do not make it not a fact. Some facts are unpleasant. That does not make them false. This is exactly why (without debating the validity of his hypothesis) Al Gore used the phrase "an inconvenient truth" for his book.