The thoughts that most conservatives have about reparations generally is either in the camp of thinking that whats in the past is in the past, or that due to disproportionate representation of black people on the welfare roles that we have already paid. What neither of these take into account is that fact that the idea that slavers went to Africa and rounded up a bunch a free men to use as slaves is almost entirely a myth perpetuated by the book and the movie Roots (which was both fictionalized and plagiarized by the way). The truth is that in almost all cases American slavers sailed to Africa where they met up with African slavers who sold them slaves. This should be evident by the fact that the native Africans were no more or less civilized than many of the Indian tribes that Western Americans came across, but they did not conqueror and enslave them. If they had run into Indian slave traders in any kind of large numbers (I certainly can't say that it never happened) there would have been just a large a trade of Indians as slaves, but the fact remains that it was unique to Africans.
This is not to say that all white men who bought slaves were righteous. The right thing to do would have been to free them as soon as they had been purchased. But consider another case. If you came across a man who was desperate for cash and in his desperation offered to sell you his wife's engagement ring which was clearly worth thousands of dollars and though you could have paid full price, you take advantage of the situation and buy it for only a few hundred. Is that the good christian thing to do? No of course not. But on the other hand, after the transaction is made do you owe that man anything. Again no. In the same way, American slavers did not owe the slaves that they purchased freedom because they did not enslave them. The truth is that those who made it to America where the lucky ones. There were certainly some bad slave owners in the south, but in Africa to treat a slave as being more valuable than a horse was the exception.
If your still not convinced consider another example. In Nazi Germany, Oskar Schindler rescued many Jews from concentration camps. The rescued Jews basically worked for him in his factory as slaves. At the end of the war did he owe them reparations? Of course not. By acquiring slaves he was saving them from the gas chambers, and is considered a hero for it. This is not 100% analogous with American slavery, but it demonstrates the principle. If life as a slave in America was not worse than life as a slave in Africa it means that Americans do not owe former slaves anything. In fact we did give them something: freedom. Something that they or their ancestors would not have gotten in Africa where the slave trade is alive and well to this day.