I am sorry that you are hurting and maybe there is much more adding to your situation that you didn't let us in about, but what I am reading here ... everything that I am able to feel when reading about your story is just: That's wrong. So wrong.
Yes, he is right, you should accept your partner for what he is, but where is his acceptance for what you are?! For what you feel? Where is your acceptance for what you feel as well? You are suffering, he does what he wants. Sorry if this is offensive, but I question his feelings for you. And I question his ability to see what he is doing to you. This may be caused by your own incapability to handle your feelings. You aren't able to get through to him and tell him what you are feeling, as it seems. If he understood how much he is hurting you and still continues, you should seriously reconsider if this relationship is worth it.
You can call what you are doing however you want, giving things a name doesn't validate them. If it causes you hurt and pain, don't do it, find a way to compromise (together!) and start having an relationship that is healthy and beneficial to you.
If that isn't possible, think about why you are staying in a situation that isn't tolerable in and of itself.
Best wishes, Phy.
Facts: 30, female, bi, v-type relationship with Sward (husband, straight, mono) and Lin (boyfriend, straight, mono), poly-fi and co-primary.