LOS ANGELES—The only public hearing to be held on California's most contested ballot initiative turned into a de-facto debate Thursday on whether gay marriage was good for children raised by the couples. The hearing focused on Proposition 8, a constitutional amendment on the Nov. 4 ballot that seeks to overturn a state Supreme Court ruling earlier this year that allowed same-sex unions. Jennifer Roback Morse, president of The Ruth Institute, which promotes traditional marriage, said same-sex unions violate the "child-centered institution of marriage." "Mothers and fathers are not interchangeable," she said, adding that gay couples should not wed because ...