"Okay, fine. That's not a good counterargument. It still leaves you with the problem that there's no evidence that marriage was created to provide an environment in which children are raised. Therefore, there is no reason to deny it to some people based on their supposed inability to raise children."
Which is already done to an extent.
You can't marry close blood relatives, technically you could produce children but they would carry a huge chance of having defects, plus it would just break down family ties, not something that should be socially acceptable even if legal.
You can't marry total strangers for the purpose of getting them into the country. It's a criminal offense which again suggests that marriage is not just purely based on consent.
As for marriage not being about children primarily, virtually no culture, no major world religion, no secular philosophy (at least before the modern left came along) ever had that idea. Marriage was always an implicit public statement that you intend to start a family. Not even atheist philosophers (again, before the modern left came along) ever suggested that marriage be expanded to an entire class of people that don't have and cannot have children. This is purely the invention of progressives who either don't get what marriage is about or don't care.
"So you're not discriminating against gay people because you hate them, you're just discriminating against them because it's easier than being fair on everybody."
This is about the institution of marriage itself, so far it has served its purpose even if a minority of couples either didn't have children or didn't want to have children (and some did it anyway regardless since as it turns out, birth control isn't 100% effective, luckily the child won't be fatherless or motherless). Even though a minority of men and women are incapable of reproduction, it doesn't change the nature of a male-female union. There are humans with missing eyes, but we don't therefore claim that human as a class of people and as a species has between 0 and 2 eyes. That's dumb.
Okay let's flip that on its head.
Why is it fair (or moral) for millions to pay taxes in order for some strangers to get various government benefits, all for no other reason than the strangers fucking each other and promising to keep fucking for life? I'm sure that's great and all for them, but that alone doesn't benefit us. If a portion of my taxes are going to that, then I expect something worthwhile in return (like the perpetuation of the human species at the very least, something that traditional marriage more than provides, even if a minority of these couples aren't having children)
I've already said, I might be willing to entertain this notion of "gay marriage" if at the very least any aspects of the legality that can be classed as "positive rights" are removed.
"...which would be symbolic discrimination, a fpoint which has been repeated ad nauseum."
Dude, there are already different types of organizations that are treated differently under the law based on what they're about. A perfect example would be nonprofit vs. corporations and I doubt either would complain. Civil union - marriage distinction could be quite helpful if the provisions were properly defined and it wasn't used a staging ground to push for more marriage subversion like in UK (civil union was basically identical in all but name, but the left still wasn't pleased). Gays get to simplify inheritance or whatever (though as I've said, anyone should be able to inherit from anyone, Bill Gates giving his wealth to a hobo - don't care), the institution of marriage remains intact.
For something to be discriminatory it has to be unfounded otherwise not being bisexual would be discriminatory too. But the union between a man and a woman is very different from a same sex union. Only one has the potential to reproduce.
Then again I'm probably arguing with someone who would claim that gendered bathrooms is the same as colored bathrooms. The LGBT agenda is ultimately a rejection of male/female distinctions, even if they are grounded in biology.
"I didn't say anything of the sort. The point is that in order for an unmarried couple to have the same ability to divide property as a married couple, they'd have to spend time and effort to create a framework that the married couple gets for free. To deny that assistance to one group of people and provide it to another for completely irrelevant reasons is discrimination. Why is this so hard to grasp? "
They would face the exact same barriers I would face if for example I wanted to co-own property with a friend for whatever reason. I could do that, maybe there's too much bureaucracy, but expanding marriage rather than changing laws or civil unions isn't the way to go.
See why it's a bad idea to expand marriage to include more and more things that have nothing to do with starting a family and raising kids?