As a kid, I used to get Martin Luther and Martin Luther King Jr.’s names mixed up. Actually, I imagined one was the other one’s father. That the “King” one was the Dad. Blame it on growing up Lutheran and the fact that both names shared substantial storylines in my six-year-old head. Ironically, and somewhat unintentionally, I spent some time with both Martins over the last two days — watching MLK videos and reading from “Letter from a Birmingham Jail” and visiting the awesome Morgan Library where they’ve got a great exhibit on the elder Luther, a priest who defied many of the teachings of the Catholic Church by pinning Ninety-Five Theses (his rebuttal) to church doors, jump-starting the Protestant reformation 500 years ago. Even though I’m not religious, it was a thrill to see one of the old documents in real life — it’s like a bit of social media pioneering before there was social media and one of the first uses of the printing press. For anyone who works with words, it’s a powerful piece …