Their counter to that one was that we allow old people to get married long past the age of reproduction.
Too many older men like Rod Stewart have kids into their 60s...all they need is a woman who is younger than themselves.
And my counter to that is that I don't have to show that heterosexual unions ALWAYS produce children, I just have to show that homosexual unions NEVER produce children. Should we start parsing heterosexual marriage based on reproductive capability? Why? Because there are some heterosexuals that cannot reproduce, we should allow homosexual marriage? I don't think so. Because homosexuals cannot reproduce, we should start parsing heterosexual marriage? Again, I don't thinks so.
Their statement about 65 years olds not procreating is like their statement that 50% of marriages end in divorce. They like to toss it out there as if it had some meaning. The correct response to those kind of statements is to after them. Have them explain to you exactly what the significance of their statement is. And based on their answer, what actions are they advocating? Then ask them WHY we should do this. What is the motivation? How does this benefit society? This usually shuts them down, because while their statements may be technically true, they are hardly compelling arguments for what they are advocating.
Always remember that THEY have to convince YOU, NOT the other way around. Never let yourself be put on the defensive. Never let them maneuver you into a position where you have to try to convince them. That what the whole 'bigot' name calling thing is about; it immediately puts you in a position of having to try to convince them.
Remember, they are the one trying to play God. They are the ones trying to overturn 10,000 years of human history. They are the ones who are saying that we as a society are under some obligation to take two guys buggering each other and put that in the same category as a male and a female. (Remember, if they have a 'right' to get married, then you have an obligation to recognize it. How can they have a 'right', if that right puts an obligation on you?) If they want to redefine marriage, they better be able to put forth at least a dozen argument about why we should do this. Their argument need to be highly compelling, and they need to stand up under serious scrutiny. Saying that because we allow 65 year olds to get married, therefor we should allow two guys to get married.............Not even close.