http://www.wmconnolley.org.uk/sci/wood_rw.1909.html
It looks like a huge scientific blunder has occurred, and since it never was addressed, the continued use of the terms "greenhouse effect" as well as "greenhouse gases" leaves a very wide hole for reason to escape the argument. Not because increased water vapor doesn't hold heat, (the main erroneously named greenhouse gas), but that the effect of increased water vapor, (which does allow heat to be retained in the atmosphere) is labeled and explained as the same physical event as plate glass (or plastic) preventing heat from escaping an actual greenhouse.
This isn't some minor point to be lightly hand waved away, as it no doubt has been for some time. If a basic premise, a fundamental error, that is obvious, and the top scientists keep insisting it doesn't matter, it weakens the whole story. It cast doubt on everything else after you keep talking, having blithely ignored the quite righteous objection from someone who is not only questioning the terminology, but your entire conclusion. Hence hand waving it away hurts the effort, not the other way around.
Such a response does nothing but strengthen the opposition, it does nothing for your cause. Nothing at all, in fact it may well damage you.
It's not anything like the evolution "debate", which has deep roots in some divine intervention, and a willingness to ignore all scientific thought and theory, as well as credible experiments and evidence from all corners.
I've watched the video that shows CO2 in a tube preventing infrared radiation from reaching the detector/camera setup. It's a reproduction of the original discovery that certain gases absorb heat energy, and it might be that somewhere a blind mouth breathing fool denies this. But those aren't the arguments I see from skeptics. They focus on more scientific objections, like the one currently on the table, despite the fanning of hands and turning away with a one line response.
Reading about the 1909 experiment, and the reproduction of, the scientific response seems obvious enough.
Change the amounts of CO2 in the box, show with utter clarity the actual response of air with increasing amounts of CO2 in it, and include other boxes with water in it, so water vapor also is involved. Measure the outgoing radiation and show the doubters/deniers of science itself, how we know something is true.
Sure there may be all kinds of trouble getting an experiment to reveal natures truths in this matter, but that is often the problem with demonstrations of scientific matters. Certainly the small volume of air in a box won't represent the miles of air above us, so calculations of how much CO2 is needed to represent the effect would be done. Larger volumes, careful control of all variables, but certainly rather than cede the matter, strike with the full power of modern technology and show, not tell, those who may be on the fence. Instead of passing a vexing wind in their direction.