Where there are literally thousands of variations of Christianity, most go virtually unnoticed by either the public or the religious elite that keep tight hold on the reins. If a particular sect has bizarre or even illegal activities, this is not considered a problem unless it amounts to bad publicity for the church. The priesthood sodomized the choir boys for centuries, with nary an eyebrow raised, as the church could suppress talk with threats. As long as business as usual could proceed and the church dues collected, immoral and even illegal activities are tolerated. When the Mormon church became more than a single mans enclave, this raised eyebrows, not because of any illegal or immoral activities, but because of the practical nature of many of the rules, which appealed to many. Thus, the Mormons were considered a threat, and still are.
Polygamy is at direct opposition to the Christian insistence that sexuality should be suppressed and well taxed. Catholicism collects dues coming and going from their guilt ridden members, and hardly appreciates having sexual freedom under the flag of Christianity waved about as an alternative. Historically, polygamous practices developed where hardship presented the culture with widows or single women without the possibility of male protection. Extended families also traditionally have more strength, where the women can take turns attending to the children and harvest time demands can be shared by the group. Thus, many solid citizens saw advantages to the polygamy the Mormon church sanctioned, to the horror of the elite in the traditional Christian churches.