What you're demonstrating, Warden ... at least to me ... is an aversion to answer the question.
IN MY OPINION, it is because some people are good at using issues ... such as slavery ... to rub Christians' noses in them.
But then ... when the shoe is on the other foot ... and someone discovers that Mother Nature uses slavery to forge a symbiotic relationship for survival, you're "caught with your pants down," and the result ... at least initially ... is to ad hom the person making the points, because he or she is seen as a threat.
And believe me, I'm no psychoanalyst ... and I could be wrong.
But as I said before: this stuff makes good Sunday school material.