If Bill Clinton had the courage to do what he promised and sign an executive order ending discrimination against gays in the military, by now we'd have noticed that no earth shaking problems developed. Harry Truman did have the courage to end racial discrimination in the military, despite arguments identical to today's anti-gay bigotry (bad for morale and discipline, no privacy, enlisted men won't stand for it, etc.).
Nunn's kangaroo court, lopsided with witnesses for his bigoted point of view, is a travesty. But Clinton may have lost the chance to do something good because he was afraid to stand up for what's right.