Every deer I shot at in 48 years of hunting was identified as a legal deer whether it was it was bedded ,standing, walking or running. I never mistook a deer for a bear,turkey ,grouse or another hunter. AR makes it more difficult to identify a legal deer,but once you identify it as a legal deer,there is nothing unethical in taking a moving shot if you feel you are capable of making a clean kill. If you doubt your abilities than pass.