Someone who gets it!
"The "is atheism a religion?" debate, for example, has fuck-all to do with "what is a religion?"" This is a concept that I've found difficult to drive home with many "rationalists" and hard science-types in general. Many seemingly factual "debates" have little to do with facts, per se, but are a proxy for a larger issue. Climate scientists and biologists seem to be especially stuck in this rut. "We'll just give them the facts and they'll have to change their minds, right?" Bzzt, wrong! And then they wonder why they get their asses handed to them in the pseudo-debates that deniers and creationists so love. (BTW, Merchants of Doubt should be required reading for these people.)
(They aren't that exclusive. In answering one, you can address the other. if your answer to 'what is a religion' includes atheism, it tells you lots about your views of religion. That is one of the reasons I rarely debate, even with students, "what is a X". I say, write a paper on it with your ideas, but for this class, parrot me.)
As you both have said, if you want an actually fruitful discussion about something, then you set the parameters and define things at the beginning. Doesn't mean your definitions are some how "right" in a objective way, they are just "the ones we are using here. but the second you do that, you reinforce your point, nebby, that generally there is an underlying agenda which matters more than the topic at hand. "you are no better than me, cause you don't like religion, yet you have a religion all your own".
Well, my point was more directed toward the "meta-discussion" where you don't get to define terms. No matter how strictly you define "climate change," denialist partisans will just substitute "evil watermelon conspiracy" in for the phrase. If you look at most of the denialist output (as well as some of the anti-corporate hard green stuff), it's screamingly obvious that the "debate" has nothing to do with climate science, but with capitalism and the role of the market in modern society. Screamingly obvious to me, at least, but some people still seem not to have caught on to this.
People have agendas? no......
It's not so much agendas as failing to see them combined with the "We've got the facts on our side, how could we possibly lose?!" mentality. Switching back to creationism for a moment, good old Dawkins supplies us with a salient example: "If they’ve [the creationists] been told that there’s an incompatibility between religion and evolution, well, let’s convince them of evolution, and we’re there! Because after all, we’ve got the evidence." That'll make any cognitive scientist, historian, anthropologist, etc. bust a gut and die of laughter.
There are some tools to help with this, of course. I know I pulled that one with a discussion on slavery in the Bible, and the guy claiming "it doesn't really endorse slavery because it's a different kind of slavery" shut the fuck up pretty sharpish after that.
But speaking of the hard green and politics stuff, there is the episode of Penn & Teller's Bullshit! on Greenpeace (IIRC, of course) where someone actually asked a Greenpeac protester about GM foods. Even if you haven't seen it, you'll be unsurprised to hear it was derailed to "capitalist corporations are evil" in about 3 seconds flat.