One of the greatest challenges in political discussion is undefined terms. Not all terms are undefined, but those that are generally are deliberately undefined. Being deliberately undefined, it enables the speaker to shift between definitions whenever it is advantageous to do so. One such term is "environmentalist."
The term can mean anything from "someone who wants a clean environment" to a specific ideology. But if a critic uses the latter definition, those criticized default back to the former definition in an effort to use the government fallacy to prove the critic desires a dirty environment.
But if one tries to start by defining the term ahead of time, those who use the term "environmentalist" as a self-descriptor complain bitterly about how the critic is defining terms in a negative way.
The best approach seems to be in the way of Socratic reasoning to narrow down the show the distinction between hyphenated environmentalists (such as libertarian-environmentalists) and those who use the term without any modification.
The first thing to do is to ask what is an environmentalist, pointing out that by the basic meaning of the word it would indicate someone who wants a clean environment. Then point out the problem with that definition: it includes people who want one but not badly enough to do anything about it, and it includes people who want one but consider pollution the price to pay for progress.
That will get the unhyphenated environmentalist to agree that definition is too broad, and that it should be narrowed to "someone who wants a clean environment badly enough to do something about it."
This is where it gets tricky, and the critic of the unhyphenated environmentalist must stay on the offensive. The thing to do is to point out that according to most who use the term "environmentalist" as a self descriptor, libertarians are not considered to be environmentalists. Then challenge the statist environmentalist to deny that point.
If the statist environmentalist does deny that point, then the critic can call himself an environmentalist without fear of contradiction, and then put forward free market solutions to environmental problems as environmentalism.
More likely the statist environmentalist will not deny that point, meaning that the critic can now say "therefore the definition includes 'and advocates certain solutions' to environmental problems." That turns the definition into a political definition instead of concern about the environment itself. That is the definition that would be hotly denied without the Socratic lead in, and in order to prevent referring to free market environmentalists as environmentalists the statist environmentalist will have to agree.
A clear and concise definition is exactly what is needed to argue with statist environmentalists. The Socratic elimination is one of the most effective ways to achieve that definition.