In the context of humiliating someone we wouldn't use 'poop' we would say 'to shit on someone'. And it doesn't really mean to 'humiliate' it means more to deceive or to do someone wrong. 'They forced her out of her job - they really shit on her there.' Also similar is 'to fuck someone over' - 'They forced her out of her job - they really fucked her over.' or 'They're trying to force her out of her job - they're trying to fuck her over.' To 'shit on something' can also mean to be considerably better than something. 'Lionel Messi shits all over most defenders.' or 'This restaurant?! Nah, let's go to the one round the corner it shits all over this one.'

humiliating someone in another way is better than pooping on someone in my opinion.