The late Mark O’Brien, the noted disability-rights activist, writer, and poet — and a very good friend — spent most of his life in an iron lung after contracting polio at age six. He died in 1999, but is again in the news as the protagonist of The Sessions, a movie about his hiring a sex surrogate. I haven’t seen the film — and don’t intend to as it would seem intrusive to me. I am not criticizing it. But Mark’s triumphant life was about the indefatigable power of the human spirit, and I worry that the movie could unintentionally make us miss the forest for the one tree.