Good question. I can't claim more than very cursory understanding of the UMC organizational structure and rules, but from what I do know individual denominations are given extremely wide latitude in autonomy, and any flagrant apostasy is either ignored, or the offending party is merely compartmentalized as a "faction."
Conversely, Southern Baptists, who also value autonomy among member congregations, have some very strict guidelines on adherence to orthodoxy. At least two affiliated churches within the denomination were "disfellowshiped" - basically kicked out - because they either affirmed homosexuality, or were ambivalent to expressions of it in their midst without appropriate censure. One was in my large Texas city.
Correction to previous comment: “individual congregations”