I think that Dr. Kroll WAS saying to let BB walk. By saying to let "young" bucks walk he is including any deer with testicles, not necessarily only deer with horns. To spare a "young" buck, and by your definition, young deer WITH horns, you MUST first spare them as BB. Seems easily understood to me at least.

I think it is obvious that Dr. Kroll IS saying to shoot a mature doe and let BB walk.