Totally serious. Batman is firmly established as heterosexual, by more than just his actions, we've been privy to his thoughts, and this story never happened. It was removed from continuity back in 1986 with Dark Knight Returns and Man of Steel introducing Batman and Superman having never liked each other. I am so glad Frank Miller and John Byrne ended that Batman and Superman relationship. It was always more commercial than logical. Batman and Superman not liking each other is much more entertaining.