Such pastors put the carriage before the horse, and will one day have to answer to God. Even assuming there was great inequality, how does focusing on such an issue get people closer to Christ? Even if their approach worked, the result would be people having a better life on Earth before dying unrepentant and ending up in hell.

Paul didn't waste time in his letters addressing the injustices of slavery, he just said if you can get free do it, but if not, be a good slave so that you can be a good witness of Christ to those around you, including your master.