The question of whether marriage is about love or sex.
It's about both to varying extents based on the relationship. I'm still not seeing the relevance to the topic of gay marriage though, since gay people generally want to get married for the same reasons as heterosexual people.
We were talking about definitions evolving.
If I started calling a trashcan a car.
If everyone started calling a trashcan a car, it would have caught on. Definitions evolve. "Gay" once meant "happy". Not many people use the word for that definition these days.
Marriage has not changed in any fundamental way.
Your fundamentals, as usual, are as narrow-minded as possible to allow you to continue to insist that the idea of gay marriage somehow breaks the definition of marriage.
Women were once considered to be slightly more than chattels to be bought and sold, of no practical use whatsoever except in sexual reproduction, child-rearing and housework. Women were often married off before or during puberty. Even educating women was considered a waste of resources.
So civilisation has gone from being (by today's standards) extremely uncivilised (as well as stupid and short-sighted), the notion of consent and the capacity to consent has been embraced generally, what more do you need to change before you'll concede that some pretty fundamental aspects of marriage have evolved over the centuries?
People can make public declaration of commitment to each other without getting married too.
Gay people want to get married because it means the same thing to them as it does to heterosexual people who want to get married.
It also in no way says what marriage is. Why an individual wants to marry is not really relevant to why marriage exists.
If no-one wanted to get married any more, marriage would not exist (except in the history books). So yes, the "why" is absolutely crucial to the topic. It only exists because enough people want it to.