Culture shock, yeah. Well...people carry with them prejudices, traditions, and morals from their home-worlds that not all of us share, but I guess we each expect others to believe some of the same basic things we do. ...I don't know. Some people are just afraid of things that are different.

Anyway, at its most basic, I guess this one comes from the truth that two men--or two women, for that matter--cannot produce children, and in some cultures, that's what matters in a marriage, not love.