Side story: This reminds me of something that happened to my friend Jill. She was dating this guy, John, and spent a day at Christmas with his family. This being the Midwest, the weather turned horrible and there was literally a blizzard outside. Her original plan had been to drive to her dad's house in another town (different suburbs of the same city) to spend the night, but seeing the weather, John and Jill asked if she could spend the night at his parents' house--she would be sleeping on the couch in the downstairs living room, while everyone else was in their bedrooms upstairs. The parents said no. They were very conservative and apparently felt that just her sleeping under their roof without being married to their son was too much. So they sent her out into a blizzard. Thankfully, she was able to drive safely to her dad's house.
Although as I said I totally support a homeowner's right to kick someone out of their house--you just don't send someone out into a blizzard, when that someone hasn't done anything bad to you. Five minutes ago Jill was a welcome holiday guest and potential part of their family, but now she's a pariah who must be booted out into a storm? That's not right.
What happened between Jill and John after that? were there any repercussions?
Jill and John went on to get married, which they still are, and they seem very happy. They do live on the other side of the country from his family and don't come back to visit very often. A few years ago his father passed away and his mom and sisters seemed to loosen up after that, so maybe it was the father's opinion that was so strict before. At the time I was pretty appalled on Jill's behalf and didn't think much of John for letting this happen; but they seem to have worked it out between them, and that's the important thing.
On the main subject, I am leaning more towards confusion caused by the nebulous nature of Girlfriend's condition. As others have said, if even Boyfriend, in whose room she was staying, didn't realize how bad she was until she got up to leave, it seems unlikely his parents would have understood it. As Hmmmmm suggested, sometimes people just have trouble empathizing with pain they've never experienced, and maybe these parents were also leaning towards disliking Girlfriend due to the various misunderstandings anyway.
I feel like Boyfriend is allowing his parents to be overly involved in his life. Economics is a powerful thing, I get that. But I don't think Boyfriend can have it all at this point--he wants to live with his parents (client base, acceptable rent level) but also deepen his relationship
with Girlfriend, who lives hours away, and whom his parents don't like.
If he were living separately from them I would say that he should distance himself from them physically and emotionally for a while, then check in and see if they are ready to really listen to him about the life he wants to have with Girlfriend. But in this case, he physically can't
get far away from them and they're always going to have more knowledge of his comings and goings, more opportunity to make judgmental comments to him, etc..
It's unfortunate, but I think he has to make a choice about who he wants most in his life--and it would be really difficult to choose Girlfriend, while still living with his parents. Optimistically, I hope his parents can come around someday, but I think it's rather tough to show them that he's an independent adult with his own life--to set that boundary with them--if he's still living with them.