So God has in times past selected peoples of certain lineage to bear the responsibilities of His priesthood (sure you can call that discrimination if you want). That does nothing to deny people of ANY lineage or race the blessings of salvation. God doesn't condone intolerance towards any. All are His sons and daughters. He simply choses who will bear the responsibilites of his priesthood. I see nothing wrong with that.
I'm pretty sure that people of all races can become ministers. In fact, we are all ministers if we believe in Christ.
Based on the context of the entire Book of Mormon, this is clearly referring to the mark of the curse. Righteous Lamanites were equally entitled to all aspects of the gospel. There were even Lamanite prophets as I'm sure you know.
Which makes it even more disturbing, imo, that there was racism for so long within your church.