Does sexual fidelity play the same role in same-sex unions?
   English: Maggie Gallagher at the Cato Institute (Photo credit: Wikipedia )     Dear Marriage Supporter,   The guys at Oxford University Press  are no dummies. When they needed someone to make the case against same-sex marriage as part of a Point/Counterpoint series, edited by James Sterba of Notre Dame, they went straight to the top: to one of the best, the brightest and most articulate spokespeople for marriage in America.   They asked NOM's own co-founder, Maggie Gallagher , to spar with Prof . John Corvino (who co-authored the book and writes the pro- gay marriage  arguments).   The resulting book,  Debating Same-Sex Marriage  was released this week, and today I'm heading up to Manhattan to watch the book launch. Live from New York: It's Maggie Gallagher and John Corvino "Debating Same-Sex Marriage." The two of them will be "Conversing" (with a capital C) with David Blankenhorn  on the marriage debate: what it means, why it is hard, and why it matt...