If you get your philosophy from the Huntington Post on serious societal issues, then don't attempt to debate the issue. Fact is that thru the centuries that one man/one woman unions were the norms created by most societies as a process of evolution and the family of the one man/one woman was found to be beneficial to the overall society.
So just stop the politically correct b.s. and go read some books on sociology and development of society. It will give you a better insight to your understanding than quoting the Huffington Post or the dictionary or Wikipedia.