This is a tough one to call.

To me, if the deer is in distress or has the potential to become in distress due to an injury or deformation, then I would probably try to kill him. Not because his "genetics"are inferior but because I had the chance to take out a hurting deer.

The other side of me says to just treat him like any other deer and shoot if I like what I see or let him go. Nature has a way of dealing with deer like this, not always the prettiest but effective none the less.