That's just it.... you know your preferences, but who can begin to guess the preferences of others? How strong is the resistance of someone born to an alcoholic mother? Generations of alcoholism suggest that just like heroin, a child can be born an addict to alcohol. I wouldn't want to run around in life knowing I was the one who gave such a person his first drink, would you?
You may think I'm just trying to manipulate this issue, but we all know we have no way of knowing the odds of actually doing such a thing. Are our private beliefs so important that we can risk gambling with other people's lives? Just like Jesus, shouldn's our thoughts & concerns be about "others"?