khsadjfh okay looked him up: he showed up at their house because he read Purposes of Love and wanted to meet her. Julie was pretty sure he had, quote, "shown up with his toothbrush," but he was not at all put out to find that she was taken and apparently the three of them were all friends? despite, well, this:

He explained that with diseases like cancer, still largely inoperable, it might be possible to project love to the patient as a form of therapy. It was faith healing under another name, and it was soon clear to Julie that he had come to Bristol in the hope of trying out these theories on the author he so admired.

Which. What??? he didn't know in advance that she was living with a female partner, he just read Purposes of Love and was like "love it. also, I could fix her."

However, Sweetman's take on Robbie's role in TFYL is somewhat different-- that while she's fundamentally sympathetic to him as a friend, she's also pointing out his flaws:

As a junior, Mary had accepted the hospital's belief in its superior wisdom, governing the sick like helpless children, controlling their treatment, releasing them when the system decided. Now she was beginning to have doubts about this misplaced 'scientific' approach, especially when dressed up as 'doctor knows best.' it touched on her relationship with Robbie when he came to stay with her in Oxford. He was still full of enthusiasm and convinced that brotherly love in the form of Communism was the only solution to the world's ills. What she found harder to take was his increasing certainty that he had found in healing through love a way of curing people which set him apart from the rest of the medical profession. When he had first set out these ideas, they had seemed amusing foibles, a refreshing change from most doctors. Now she was no longer sure they were harmless. Far from liberating the patient, such psychological 'tricks' could only increase the doctor's control. it was beginning to look like dominance masquerading as love and freedom.