I'm more concerned about ethical shots than ethical calibers. If your going to use a small caliber than you must know its limits. I have took several deer with a 22-250 and .222 so has my son. But you have to be prepared to let deer walk if the right shot doesn't present itself. A deer shot in the heart or lungs can not live long, but you have to make sure your going to get it there. To each his own, use what you want but be responsible in doing so.