My boyfriend spanked my kid (shes not his)

So earlier we were at my boyfriend's parents & his mom, his 3 year old niece &, my 3 hear old daughter were playing. Well my 3 year old bit his mom playing around not being mean and she told us so I took her upstairs and had a talk with her (my kid) about it and he came too and he spanked my child really hard because and I quote "your kid bit my mom". I grabbed my kid and my stuff and we left. Do I have a right to feel upset at what he did? I cant stop crying mind you I'm 6 weeks pregnant I expressed that he is not to discipline my child