Last time i checked the difference's between races were very insignificant, while the difference between the genders are very apperant. Differnces that are reconized from the basic biological level, through society, and even in our court systems. Supporting that dichotomy is what marriage has been for thousands of years.
They weren't insignificant to millions of Americans who fought hard to prevent integration.
It's all relative toyour bias, isn't it? If I put a black man next to a white man, you can see the difference; a straight man next to a gay man, you may not.
(Though I hear some claim to have a well developed "gaydar" detector).
You have two mature, adult human beings who feel the same type of biological urges of attraction, sexual desire, and who fall in love.
Aren't the similarities between those two people a lot more similar, gay or not, than they are different?
Let's face it: you are now going to not ask the question honestly, by drawing a conclusion from the facts. You are going to start with the conclusion that there is some difference between the two justifying discrimination and frantically try to identify it to justify bigotry. You see this a lot when people respond to this by saying "but a man and a woman can have children, and a man and a man cannot! That's the reason!"
You then point out that a man and a woman who cannot have children - hysterectomy, elderly, etc. - can still get married.
Darn, they say, that's right, and they race off to look for the next difference to use to justify bigotry, without noticing what they're doing - looking for reasons to justify a conclusion, not forming a conclusion based on the facts. And they don't even realize it themselves, but they are motivated by bigotry. Otherwise, when 'the' reason about having children is rebutted, they'd say "oh, ya you're right, ok I'm changing my position". That's not what you see. The position is for darker reasons.
What are those darker reasons? For many, it's just a visceral reaction against gays, because the idea of gay sex is so repulsive; not a rational opinion about human rights.
It's also that many have decided that *they* are moral by rejecting gay rights, and to allow gay rights would be like allowing rape - they would feel they had become 'evil'.
It's emotional, not rational - in their battle to be 'moral' they have chosen the immoral view.