Let's stick with your first topic which is all about hunters and what they choose to use as weapons. Hitting animals with vehicles does not fall in the same catagory. An accident is an accident, unlike mother nature, a human was involved yes, BUT the human usually has no control on the outcome.
If the bat gets the job done quickly and effectively, then it sure seems ethical to me. I guess you must be able to fly to get that close to a duck with a bat