Husband won’t accept my sister because she’s a lesbian

My husband and I have been married for almost 8 years. He is more conservative as far as political and social views, while I am more socially liberal I guess you would call it. We have 3 boys from PreK to freshman in high school. The issue is that my sister let the family know she was dating a woman about a year and a half ago. She had already talked to me many times leading up to her ‘announcement ‘ because it was a transition for her, she had always dated men and now had feelings for a woman. I personally believe love is love, and fully support her and her partner. My mother and husband have a hard time with it because religiously, they believe it is a sin. Our family always spends Christmas together at my parents, and last year my sister did not come because her partner was not welcome. My parents have finally met my sister’s partner, and we will all be together again this Christmas and I am very excited. We have a house near my parents that we stay in when we travel there. It has a separate bottom level that you must go outside and up the stairs to access the top level, where we stay. I told my sister that she and her partner could stay in the bottom level during Christmas (while my family would be on top level). Well, my husband returned from talking to my sister only to tell me he will not be allowing them to stay there. He says he doesn’t want our kids around ‘it’. He says it’s ok if it’s just my sister, but not both of them. We are talking about grown women, 36 & 42. Very kind and respectful individuals. I can see that I should’ve discussed it with him first, but I honestly did not think there would be an issue. I thought everything was moving along and we were all getting to a place of understanding, if not acceptance. Of course we are in a huge fight about it, with me feeling like I should stay somewhere else with the kids if he can’t accept my sister as part of our family and someone our kids should be around. Her partner too! They are both wonderful people and I want my kids to know them and spend time with them. My husband will not budge, he is so stubborn and takes his perceived role as ‘head of the household’ very seriously. I’m just so upset that we are having this problem in general. His views on a lot of things and unwillingness to be open minded at all causes a lot of stress on our relationship. I’m just at a loss at this point.