I'm not saying respond in kind, just be firm in your convictions, and/or at the very least, ask them not to bring up the subject in your house while they're YOUR guest.
my $0.02
Its actually easy. You just smile and say, hey, you're talking to the wrong guy(girl)... I love Sarah. Say it sweetly with a smile and it puts it back on her.
I was talking to a black preacher some time back who went off on a rant about Condoleeza... I don't agree with everything she ever did but his attack was uncalled for... I said with a smile, hey I love that lady, she's one of the smartest people out there... it caught him completely by surprise and he started backpedaling right away. I just kept smiling. In his world he never imagined anyone actually liked her. And probably in Dalton's world she never imagined anyone normal likes Sarah. Its the opposite of course, normal people are drawn to her, they recognize her as a kindred spirit. Not perfect, but good and decent.
Absolutely spot on. One of the oldest tenets of civility. Do not be rude in someone else's house - nor allow someone to make you uncomfortable in yours.