Some who support female bishops are against the measure because they feel it is too discriminatory because it still allows parishes to reject female bishops. While it is believed that the traditionalists do not have enough support to block the measure, those in favor of approving the measure are worried that the controversy may prevent the issue from passing.
I remember a time when the very idea of female bishops would have been laughable. Now the biggest point of contention is that allowing female bishops is not progressive enough.