Well, think about this: the early Christians thought that John was not going to die, but even he understood differently (John 21:22, 23). From what I know, slavery is not a sin in the Bible. Philemon had a slave (Philemon 16). Paul didn't say to set him free, but that he should treat him like a brother. It's not really whether the Christians had laves or not that you should be looking at, but how they treated their slaves. Because, it Is not what is popular at the time that determines a Christian or not. But, it's the fruits that we bear that determine if we are Christian or not (Matthew 7:16). Compare those professing Christianity to Galatians 5:19-23. If they show more along the line of fruits of the spirit, they are Christian (John 4:24). Otherwise, do not believe them when they call themselves Christian.