here is some proof in the form of Benton/Fenton.
I am not picking on the dog’s owner. I have been in the same position (more or less) with my first Springer Spaniel. Bonnie would take off after any bird, rabbit, rat that caught her eye. Fortunately we never came across deer with her, and for some reason sheep did not turn her on. I think you learn most from the dogs that behave worst; mostly because you have to think about the problems you are having to deal with.
Anyway, over to Benton for those of you who have not seen him… you may like to turn the volume up to see if you can make out all the words as you find out why train your dog to stop?