Hasn't the Church been responsible for much injustice?

This is true. It is more true than you know. It is probably safe to say that everyday and nearly everywhere, several persons who belong to a church are doing something contrary to the teachings of Christ.
Carrying this further: a study of all churches in history and across the world now will show a great diversity that reflects the indigenous tendency of a church. For example, American churches are somewhat different from churches in Mexico.  Also, there are stances taken by Episcopal churches in America that are rejected by the Church of England.
One major difference of culture and church has been over the matter of “union of church and state.” European churches have reflected the Roman history where church and state were merged.  American churches reflect the Revolutionary War history and there is a separation of church and state.
The worst examples of the Church being responsible for injustice were performed where the government was free to use the Church as a cheerleader for its political agenda. These atrocities do not represent a pattern in church history precisely because they are not typical of the teachings of Christ.  Christ does not teach us to harm either our enemies or our “Samaritan” neighbors (those who are different).  The Church includes all nations, united by a common bond of faith.

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