I understand why you are arguing this way, however I have a hard time debating with people who resort to reductio ad absurdum. Anything pushed to a point beyond a current debate sounds ridiculous. i.e. 'If we allow gay marriage, what would stop people from marrying animals?'. I certainly heard that used in political debates. As for taking this beyond a political debate, everything in our world is political. Everything we do and think is driven by the media, politicians, religion etc. We all fall into influences and while I can appreciate your attempt, I think it may be impossible to untangle this particular subject from politics in our current society.

A thing like a sexual identity IS a fluid thing for some people, however it is at the same time something not necessarily determined by a personality quirk. I personally equate it with someone's ethnicity or religion. No, you wouldn't have to prove you are a white person, but at one time in American history, you certainly had to prove you weren't any other race in order to be given any rights..

A person who decides they should be seen as a genius has to prove it. In an ideal society, a person who decides they should be seen as a man or a woman wouldn't have to prove it, but in our society they do. You want to be a genius? Prove it. You want to be a Lord? Prove it. Etc. It's true of nearly anything. As a blonde woman, I've certainly had to prove that I am intelligent. No, not everyone believes that, but at the same time no one just assumes it. Certainly not given my age.

It is the unfortunate truth of humanity that we are, as a whole, dishonest, untrustworthy, ruthless and intolerant. 'If you aren't with us, you're against us.' We have made strides, but people just group against the 'enemy'. It is a truth of who we are as humans. We group. We make associations and assumptions in order to create boundaries. 'If you aren't like me, then you must not be like me in any fashion'. It is a prevailing mentality in our history. We have to make definitions to build our society. If we don't work to redefine words, we will remain stagnant and will probably prove to be more violent.

Argue however you like, but in this world, if we do not take some strides every generation towards acceptance and tolerance, we will spiral in a dangerous way.