The real reason is the writers couldn't get Joan and Morse together so they basically ruined Joan's character. In seasons 1-4, I loved Joan. She was funny, fashionable, flirty, and smart in a way that Morse isn't. Their banter was the best thing about the show. So, they had to destroy all that with this stupid falling out with Fred and turn her into a typical sixties era TV cliche. Plus, I don't think they're doing a very good job of hiding Sara Vickers' pregnancy and that is distracting to me. Two episodes in, and Joan is really annoying me.
Agree. That bit was stupid. Two kids being taken away from their parents would not say that even if their parents were immature weirdos.