Since you mention Christianity, here is an example of the transformation power of introducing new memeplexes on the practice of killing cursed ("mingi") children:

Missionaries first came to the Banna decades ago, and the Christian church here is larger than any other among the tribes of this region. Still, their numbers are small; Banna's Christians make up just 1 or 2 percent of the tribe's population.

But their collective efforts have been enough to almost eliminate mingi killings within their tribe. With little money or other means of support, Banna's Christians have accepted responsibility for nearly all of the tribe's mingi children. Many, like Kaiso, are already caring for one or more mingi boys and girls. One family has taken in 17 foster children.

Whether the slow end of the killing of children because of superstition constitutes objective working or prosperous society is a matter of debate (population growth and all that Jazz). I find it hard to deny that this kind of "cultural imperialism", seems right to me.

Much like, and this goes partially against my principles, I wouldn't mind, in a different branch of our universe, forcibly converting modern day Aztec's still sacrificing thousands of people to the Sun each year to Christianity (or Islam for that matter).