When I first began to read this, I thought I was reading a screed, some guy venting his anger. But after getting into what he was saying I realized I had misunderstood (I think Frank Zappa threw me off). His objections are very similar if not identical to my own although worded a little more passionately that I might have done.
I have to add, that increasingly I have been spotting on the web comments and blog posts that seem to give a more positive spin to slavery. This is vile beyond words. Slavery is not comparable to industrial conditions in Northern States, it is not preferable to life in Africa, and if you think bringing people to God is a laudable goal, slavery is still overkill.
Give the attached post your attention, there are some outraged but good thoughts therein.