The precedent was set years ago. Geraldine Ferraro was at the dinner when Cardinal O’Connor was the Archbishop of NY. (I remember of photo of her shooting daggers at Cdl. O’Connor, who made no secret of what he thought of her act, though not at the dinner.)
Since politicking is not supposed to occur at the dinner, it is not the same as outright promoting a candidate who is pro-abort or even providing a platform.
Truth is, the dinner would be pretty sparsely attended with no pro-aborts. Maybe it is time to end the dinner, lest the church be tempted to play towards Caesar.
I think you're right. If you can't have the event without cosying up to supporters of infanticide, then just don't have it.