G.B.F. is a good-natured teen comedy about prom queens in search of gay best friends. Its depictions of affection are chaste and its language is clean. So why does it have an R rating?

"You don't sound like the ones on Bravo," says the blondest, hottest girl in the school, Fawcett (Sasha Pieterse), to the guy she is tying to woo, Tanner (Michael J. Willett). Tanner is freshly out of the closet and the coveted accessory of his school's three most popular girls, to whom he compares "warlords in a…