Complex sentence: He was censured by his Conference, but that censure was overturned by the 1840 General Conference--which then bowed to Southern pressure and passed a resolution prohibiting the testimony of Negroes in church trials within states that forbade such testimony in public trials.
Split into simpler sentences: He was censured by his Conference, but that censure was overturned by the 1840 General Conference. The General Conference then bowed to Southern pressure and passed a resolution prohibiting the testimony of Negroes in church trials within states that forbade such testimony in public trials.