Quoting Bible does not make argument infallible
This letter is a response to Andrew Mead's letter, "Bible is standard against slavery, gay marriage" (SN 2/27). Contrary to Mr. Mead's letter, slavery and other activities that humans choose to regulate may be consistently claimed to be wrong based on moral principles (including, and I know this may come as a surprise, those principles outside the Bible), philosophy, the decency of man and even other holy books.