You cannot compare apples with oranges. We are talking about marriage here, that is done in good faith with the consent of all the parties, including the girl in question as I believe that the bride has to islamically agree to the marriage. Marriage is a sacred institution. This is something that the religion plus nature and the law are allowing. Marriage is not a crime, whereas some of the other things that you mentioned are illegal. If it does not harm any third party, is done with the consent of all the parties and is not illegal then I say that their cultural norm should be respect. We should not indulge in cultural imperialism. First of all you need to start looking at the society that you live in and all the cultural ills there . Then you should try to address them before you start lecturing others abroad how to live their lives. Seeing things through others cultural perspective we are the barbaric ones. If we want others to change their cultural traditions then we should first do some changing at home, otherwise we have no right to talk.