This is not about “encouraging” Deanna to have an abortion here and now which is bad enough. This is about ordering her to have an abortion, something that is completely unacceptable and immoral.
It wasn`t even mentioned so far that Deanna was facing the choice between resigning and following this order. Dr. Ree was overruled by Riker but that doesn`t change the fact that a Starfleet doctor legally has the right to demand this procedure against the will of the woman in question. I find this incredible.
I wonder what the outcome would be if Deanna would fight this on the basis that demanding her to undergo an abortion is against her sentient rights and therefore an illegal order. As I said, how was that to work in practise? Stunning Deanna or dragging her by force into sickbay?
When Deanna went on this mission, I had reason to believe that Dr. Ree was carrying everything he needed to look after her with him. I am sure Riker would not have allowed Deanna to do so if it would have been a “suicide mission”. There were risks but within acceptable limits. I can`t find that part of the book right now but I think I remember that Dr. Ree was assuring Riker that Deanna`s condition will be manageable during the mission.