It is sad to hit any animal, but it is worse to have a serious accident trying to avoid it....which nearly happened to me.

Many years ago...(35? wow)...I was asked to drive a friend who had vision problems to an appointment about 150 miles away, using his car...a VW Beetle.
   One the way home, after dark, we were buzzing happily along, singing & joking, when an opossum ran from the right side of the road toward the left. My friend, even with one eye bandaged, saw it about the same time I did.....and grabbed the steering wheel! Not only did we hit the 'possum, but the little car swerved violently to the right, then the left, as I tried to compensate for it all.
Fortunately, after another smaller swerve to the right, I managed to get it back in my lane and decided it was okay to breath again.
I don't suppose the whole thing actually took more than 4 seconds, but it was one of those slow-motion '27 thoughts about many things' moments.
After I calmed down, I suggested to Tony that the driver might best be left to deal with such incidents in the future. He...ummm... agreed.

So....there is a big difference between a possum, or a dog--- and something like a deer. It is a good idea to tell yourself in advance, hoping you never have to decide, what you should do.