The error in your statement lies in the phrase "comparison that you are making between racism and gay marriage as a civil and human right" is the word "gay".
Marriage is a civil right to all races and all genders, and that includes "mixin'". Races, same or mixed; genders, same or mixed.
What is the source of this "civil right", aside from the imaginations of the people who assert it?
Marriage is a fabrication of the feudal age for the purpose of determining property rights and inheritance, an institution in which the state has an interest because of the necessity of adjudicating who gets what as an inheritance and how much of it gets taxed. It's not biblical, but its biblicality has been asserted in latter day "translations" of scripture, just as divine right to rule has been.
In these days where divorce is just as common among heteros as marriage is, the state has an interest, therefore, in non-traditional marriages and partnerships, again for the purpose of inheritance rights and taxation.
Wait a minute.... You're claiming that marriage is an artifice of the medieval era? ? ?