I just find it difficult to comprehend how someone can care about an animals extinction but not about the systematic slaughter of animals but each to their own. I won't use the word environmentalist anymore though if it hurts your feelings despite it meaning people who care about the protection of the environment which I believed the majority of people here were concerned about and have stated. I don't think it's something people adhere to. As i say below you can eat meat in a sustainable and ethical (to an extent) manner, but people don't and buy into an industry that is inherently wrong for a multitude of reasons.
You don't understand because you choose not to listen, though. I've told you one reason and your only response is to shrug rather than engage. You have to really believe that your view of the world is so righteous, so well formed and so uninhibited by the petty problems of normal people to not even engage with alternative perceptions of the same problem. Which is the problem I have with the environmentalist label, on the context you've used. It becomes prescriptive, and a stick to beat others with when you have similar views of the challenges but different views of the solutions.
Here's one problem with your snarky statement, and the attitude underpinning it. The reasons for the rapid move into a mass extinction event are varied. We can say conclusively that human activity is one of the key drivers of it - and it's now uncontroversial to say it's the most important one. Within that, the factors are manifold. Habitat loss driven by our desire for more food is one of them, and meat is a significant part of that. However unfortunately our desire for vegetarian food is also a significant part of it. There are all sorts of other non food products driving it too. And much more besides.
Your lifestyle contributes to this habitat loss, for reasons you're both conscious and unconscious of. The extent of your knowledge is limited and always growing, and as that happens, you'll discover more ways that you're harming the planet.
So, using your logic I could say "I just don't understand how a supposed environmentalist can eat x, use y and demand z. Does he really care?" on any range of issues, including the one you chose to raise: animals. I find that incredibly unproductive, more than anything. Your very existence is a burden on the planet, based on the conditions you were born into. There are no good choices, at this point. Just less bad ones. Some of the things you'll do are good, some of them are bad, some are both simultaneously. Barros has very helpfully pointed out one example of it. Unfortunately some renewable energy sources will be one of those factors that contribute to the extinction of some species. I do not think that people who advocate for wind energy are betraying their belief that mass extinction is a bad thing.
I think this demand for perfection, and the desire to point out imperfection, is a significant problem with "environmentalists". It makes it easier for someone like barros to shrug his shoulders and point out that this idealistic environmentalists still can't find their perfect solution they keep striving for. It makes people dislike some of the values that the movement upholds, and thus less inclined to embrace it or be embraced by it. It wastes time. It's not all bad, obviously. As people gradually move closer to perfection, they're doing some good. It's clear that chastising people for bad behavior is one of the most effective forms of social control, which can lead to social progress, and hard-line attitudes to what constitutes bad behavior play an important role underpinning that.
I just don't think, overall, it's the best approach to achieve the goal. The alienation it causes is particularly unhelpful when the goal is so universal. However that's just my opinion from a very limited vantage point, limited experience, plenty of ignorance, and in a situation that is very hard to think about in a clear-headed way. I am mostly probably wrong about most things, because it's a combination of very complicated environmental, social, political, legal and economic factors that are impossible to have the required understanding of, simultaneously, to understand the problems in their entirety and propose perfect solutions. So I think imperfect solutions are things to be very happy about. And when comments like yours are made, yes, I find it sad, in part because it's a reminder of how some of our biggest challenges to making progress are so fundamentally human.