I think it's a mistake to say point-blank that people are trying to kill the two-stroke for the environment, so to hell with them and the environment. I think the proper approach is to say that, yes, two-strokes do for the most part create higher emissions than four-strokes on average and when using the 1970s technology that all motocross engines seem to be frozen in. Then at that point, you can easily transition into talking about how 21st-century two-stroke technology is, indeed, as clean as or cleaner than modern four-stroke technology. If Honda says they stick with the four-strokes for the environment, the proper rebuttal is to point out the two-strokes that THEY INVENTED which were cleaner than their own four-strokes, and which they quickly swept under the rug. That's where the real juicy rhetoric is.
You'll never get anywhere with environmental Nazis by making the dichotomy between two-strokes and the environment seem stronger. Even if you think global climate change is a "lie" or whatever, it's in your best interest to point out the fact that a modern two-stroke is not a highly-polluting machine.