The Bible does not "support" slavery in the sense that it demands it or even encourages it. It simply recognized it as being part of the culture in NT times and give appropriate instruction as to how it should operate within Christian principles and morality. The fact is there were indeed slaves and masters existent in their culture and the Apostle Paul deals with that reality by speaking both to slaves and their masters as to how they ought to live within their respective roles in a way that would honor Christ as their Lord. To say that this is tantamount to "supporting slavery" is a gross misstatement. As you know, the abolition of slavery in this country was due in large part to Bible believing Christians.