Gay Rights

If the Declaration of Independence says:

"We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness."

Can we even legally say that gay marriage is illegal if it's in our Declaration of Independence? Because if all men (and women of course) were created equal than we cannot say that one group of persons can't have the same rights as another group because then our Declaration of Independence would be null and void.

Well at least that part of it, and possibly other parts.