CoC on Joseph Smith and Plural Marriage
This is part of a much longer answer to the question which you might find interesting. They acknowledge their historical denial of Joseph's polygamy and say that even if he practiced it, it was wrong.
What position does Community of Christ take on Joseph Smith Jr.’s alleged involvement in polygamy?
Our faith is grounded in the gospel of Jesus Christ and not in the actions of any particular person. The Community of Christ affirms its long history of vigorous opposition to polygamy as a doctrine or practice, regardless of what historical research may ultimately conclude about its origins in the early Latter Day Saint movement. The church has consistently taught monogamy as the basic principle of Christian marriage (Doctrine and Covenants, Sections 111 and 150).
As a policy, the Community of Christ does not legislate or mandate positions on issues of history. We place confidence in sound historical methodology as it relates to our church story. We believe that historians and other researchers should be free to come to whatever conclusions they feel are appropriate after careful consideration of documents and artifacts to which they have access. We benefit greatly from the significant contributions of the historical discipline.