Yet gay and bisexual people exist, and they ALL say they are that way naturally. Are we ALL lying?

I believe that is the whole basis of most of the disagreement-religion. People seem to forget that one of America's most important pillars is that freedom of religion. This anti same sex marraige, civil union, or whatever terminology you want to use seems to be because some people think that their religion is being tarnished because of it.
But that really isn't true. We all have our views on this subject; and whatever we think of it, we just need to accept the simple fact that there are; and always will be those that disagree with our own viewpoints. We need to accept this more; and stop thinking that we can force our beliefs upon others.
Whether a person is gay or not really shouldn't bother any of us. We just need to all believe that each and every one of us has our view, and that's it. We don't need to concern ourselves with what goes on in the bedrooms of others.

Because normal human beings no more want to marry a member of the same gender than a goat.

See above.

That I agree with. It's just like abortion. Another stupid situation that humans have legalized based solely on "rights" and not what is right. But just as abortion may happen, it's still legalized infanticide, "same sex marriage" is a legal recognition of a dysfunction.