“Fun Home,” the graphic novel that became a Tony-winning Broadway musical, was controversial upon its release 20 years ago and banned from some libraries after allegations that it was too explicit and out of alignment with religious values. But TJ Rosa and Liam Kelley, director and assistant director of this gorgeous musical at Civic Theatre, say that lots of people in Generation Z have no problem at all with the author’s coming-out story. Was the controversy merely generational?