Well, I really like how the APA was thinking here, in the proposed ban. Even though it was ultimately not carried, I liked what they were trying to do.
I'm not sure that they've read their history, though. The Methodist Episcopal church of the nineteenth century passed a ban on ordained pastors owning slaves. The first person to challenge that ban--a Bishop Andrew--was remonstrated and threated with expulsion. All this did was lead to the formation of the Methodist Episcopal Church, South.
I fear that if any such professional organization were to try to enforce such a ban (like the AMA's ban on doctors' participation in executions), we would simply find ourselves with two national professional organizations where once there was one.