Scientology, Mormonism and others religions also have a structured shunning policy in place. Religious leaders want to protect the power and control over people, at all cost and by any means.
That's a pretty cynical view of relgion, and I can tell you for a fact that Mormonism has no "structured shunning policy" established. In fact, LDS church leaders actively discourage shunning because it's more likely to drive offenders away, and the idea is to bring them back. I can't speak for Scientology, but I don't know many Christian religions that practice formal shunning. Some families may decide to shun offenders on their own volition, but I know of no Christian faith that actively encourages it...except the Jehovah's Witnesses and perhaps some Pentacostal or evangelical fringe groups like the Westboro wackos.
In some cases, the Orthodox churches practice shunning, but again it's mostly family oriented. A local priest of a Greek Orthodox church shunned his son when he married a black woman. It wasn't because she wasn't Orthodox because she offered to join. I don't even think it was entirely her skin color. I think it was more because of the drastic cultural difference. I used to like Greek women a lot, but they were only interested in Greek men for the most part. (And Greek men liked marrying blonde gals with blue eyes, but that's another story.) Anyway, the priest's parishioners brought the priest eggs to show their support and to solace him. But they didn't shun the priest's son or his wife; however, the priest and his wife and family did. I think the priest and his family were just used to Greeks and Greek-Americans. They liked Greek food and Greek music, and they loved speaking Greek. A black family, on the other hand, might serve glazed ham, mashed potatoes, deviled eggs, green beans, ice tea for the main course and pie or cake for dessert. While that may be my type of food, many Greeks would prefer eating poison! (And I'm sure the black family would rather eat poison than Greek food.)
Shunning is a natural human reaction, but only cults that are into control actively encourage it because it's an effective vindictive tool and discourages dissension.