The Convention itself didn't withdraw my ordination, but the church that did cited the SBC's "Baptist Faith and Message," the core doctrinal guidance of the denomination, in so doing.

1 Timothy 3, "husband of one wife" was the basis for this within the BFM.

It is true that each church is theoretically autonomous, but the SBC exercises a kind of elegant control with the BFM, and churches that staunchly refuse to follow it have been known to have their fellowship with the Convention withdrawn. State Conventions under the SBC have split. Local associations under the state conventions in the heirarchy have...well, you get the point.