Exactly. This would be one of main arguments against the typical "it's a consensual adult thing, what is it to you!" argument for gay marriage. In fact, to many

Exactly. This would be one of main arguments against the typical "it's a consensual adult thing, what is it to you!" argument for gay marriage. In fact, to many people, a polygamous relationship between a man and many wives would be more "natural"than gay marriage (e.g. some Muslim countries, where gayness may be punishable by death by Sharia law allows more than one wife). Same logic applies to incestuous marriage, although this would be more extreme since there are very strong taboos against it (not throughout all history, though, e.g. in Ancient Egypt pharaohs mostly married their sisters).