If the choice you're complaining about is bringing in slaves, that choice was made by the homogeneous English immigrants. So apparently homogeneity doesn't always lead to good choices. Consistently practicing the Christian values they preached might have, though. So really this is just another point for common culture > ethnic homogeneity.
Wow. Are you under the impression that Christian English settlers didn't oversee slavery in America? Are you not familiar with how they used the Bible to justify slavery? These are real basics of American history.
