I agree that this use of pollution is a slight extension of the way that the word has been used in the past, but I think it's a perfectly reasonable extension. Humans have a hard time thinking in terms of systems dynamics, in part because most of the language used to talk about systems dynamics is so complicated (in large part because systems dynamics *are* complicated).

Pollution is a concept people at least think they understand - it's bad. I'm willing to pay the price of some people not perfectly understanding how the whole system works if they are at least properly alarmed about the situation. Most people who thought they understood the problem *before* this linguistic extension are just as confused about how things really work as those who thought they understood it when they first heard GHGs being labeled as pollution. Most will probably never have a really deep understanding of how systems work. But no human changes have ever waited for perfectly accurate knowledge to percolate through all of humanity. Change is messy.

One thing along these lines that drives me crazy is the nature-lovers who are shocked to discover that the vast majority of species that have ever existed have gone extinct. Nature did not develop a perfect balance in which all species have found the perfect niche in balance with one another. Nature is a constantly changing, often destroying dynamic, which at any given time manages to have an amazing array of beautiful but temporary balances in it. Do I wish everybody understood this? Yes. Am I okay with there being a lot of people who don't, but who nonetheless give their precious time and money toward preserving as much remaining biodiversity as we reasonably can? Yes. Messy, messy, messy.

Our climate system is being polluted by an excess of carbon dioxide.

(Original context: Republicans Speak Out in Support of Renewable Energy and Against Fossil Fuel-Funded Climate Deniers)

Update: This made some sense to the person I was conversing with, and they said they'd have to think about it now. It's important to allow space, both for ourselves and others, to change our minds and develop our thinking, especially on contentious subjects.