Should a person leave their own house to accommodate a housemates date?

My sister and her ex live together. They are both on the lease and pay half/half rent. I am friends with both. He asked if she could vacate the house, as a girl he was bringing home was nervous about the idea that his ex was there. He said "do you mind if we have the house? She s feeling a little nervous" My sister said no, that she would be staying and that for him to ask is unreasonable. He then complained to me, said that she is being difficult because a guy she s seeing has a house, and "she should just go stay at his house". When he seemed annoyed at my sister for saying no. I sided with my sister and said he cant expect that of her. He said "I never expected anything or demanded anything of her, but she had somewhere else she could have gone."

So Yahoo community! Am I being bias? Is his request unreasonable? Or is it fine...? If he wasn t expecting anything, wouldn t he have said "no worries" instead of complaining to me about her response? I love them both, but I am genuinely unsure who is in the right or wrong here. (Of course I will stay out of it, but I would love to know outside opinions)