The vast majority of Blacks disagree whole heartedly that there is any parallel between their status as minorities and that of Gays. Furthermore, they disagree that gay marriage and inter-racial marriage are in any way the same thing.
Inter-racial couples fit the legal definition of marriage and always have.
Again, civil unions would give Gays the same rights. Refusing to destroy the meaning of the term "marriage" does not deny anyone equal rights. You can not steal words in order to co-opt their meaning and force people to accept your ways.
Blacks and interracial couples' opinions are irrelevant. Do you think they all are experts in jurisprudence and Constitutional Law?
Prior to Loving v. Virginia, the 'definition' of marriage was a man and a woman of the same race. They did NOT fit the presiding legal definition of the day and they DID change the definition of marriage in the US.
Ignoring the 'separate but equal' for a minute, you still cannot claim that civil unions give the same rights as marriage. Civil unions are not universally recognized by all states, and they do not in any way afford the same privileges and rights at the federal level either.
Why does YOUR definition of marriage trump that of everyone else? The definition of marriage has gone through many changes over the course of human history, yet you continue to ignore this fact. Marriages used to be about ownership of woman, they have been used to form alliances and consolidate empires. Marriages of same-sex individuals have been recognized in this and other countries. Civil marriage is merely a legal contract that is recognized by the state. Any requirements for religious marriage will not change. No one is forcing churches or other religious institutions to change their definition. This is ONLY a matter of the state.