My mom was pissing me off and being nasty and childish to my step dad. I was in the field with my horse later and she came in and I whispered, "give her hell". He promptly went up to her and bit her. And then again. He kept being super menacing to her, following her around with his ears flat against his head etc, even though usually he was the most laid-back animal ever. Eventually I went over to him, patted him and said, "leave it" and he stopped. A year or so later he kicked the ever-living shit out of a pony who slammed into me in the field and knocked me over. I was fine, just covered in mud, but once again he didn't stop menacing this pony until I went up to him and said, "that's enough now, stop."