RE: Ethical: Monster in doe season
To me, it would be no different than shooting any deer out-of-season or at night. It's illegal, unethical and just plain wrong. I've used my buck tag early in years past and then had a much larger buck come stand broadside in easy bow range (most recently last year), but I had no choice except to pass. That's the chance you take when you decide to take a buck--there may be a bigger one nearby.
Today's small bucks are tomorrow's trophies.