The bible does deal with slavery by telling slave owners how they should treat their slaves, not in saying that 'thou shalt have slaves'. By the way, Israelite slaves were of two kinds:
1. individuals who sold themselves into slavery because there was no such thing as bankruptcy court back then, or
prisoners of war.
It was not a sin to own or not own slaves. What as a sin was to own slaves for improper reasons and treat them improperly.
Same gender sex is a sin. Period.
And in that lies the problem for me. How can our Holy Creator bless the ownership of another human, who was created each and every one of us in His image with free Will condone such a monstrous thing? A well-treated slave is still a slave.
When one is owned by another they are deprived of life. Maybe not the physical aspect but of the essence of life.
Could it be perhaps that some parts of the Bible are wrong? That the words were written contemporarily and conformed to the culture of the day? I don't know. I don't have the answers.