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? ? ?
It's not a claim I'm making--it's an historical fact that I'm reporting. In the era of Constantine, only titled people married and the "droit du roi" was practiced (the king gets to screw every bride first before the husband got permission to). This didn't change until the emperor gave up land management to his suzerain kings under him and property inheritances became an issue...with the wife being part and parcel of the land assets to be handed off to the heir.
It wasn't until the 19th century that women began the quest to cease being regarded as a man's property....and the children, for that matter. Men always got custody of the children in a divorce until Child Labor Laws got passed. It was then that judicial entities regarded children as the sole providence of all women. Not before.