I love George Carlin as a comedian. I think he is hilarious and often insightful about modern culture. If you begin taking comedians too seriously though, you're libel to get laughed at.

Carlin's "argument" is that the planet itself cannot be harmed by humans. I would agree if we are going with the literal definition of planet. The piece of rock orbiting around the sun will be just fine regardless of what we do. This is true. If this is what you meant when you said that they don't care primarily about the planet then I would have to agree.

My assumption though, was that you were talking not about the condition of the rock on which we reside, but the environment (in other words the living things on the earth). Now Carlin talked about how humans aren't really responsible for the extinctions of other species, and though the points he made were funny and entertaining, they were far from accurate. Surprisingly enough, comedians don't get peer reviewed...imagine that?

So yes, if we look at the cosmological picture, nothing really matters. Humans will eventually die out and the entire universe will eventually decay until there is nothing but darkness. But here on earth, we do care, even if in the grandest sense nothing matters.

As far as the selfish part, I'm surprised you would make this argument. The entire idea of capitalism, and why it works is because people are looking out for their self-interest. You and I both know that this actually is a very good thing, because it allows for effective and efficient use of resources. The reason people are proponents of capitalism isn't because they are greedy (like far left socialists would have you believe) but because everyone benefits from it. The added bonus is that personal liberty is also maximized under a capitalist system.

Environmentalism is similar in that it looks to maintain our own self interests: making sure we don't have a shitty dystopian future where we have to wear oxygen tanks to breathe (exaggeration of course), but it also involves the moral obligation that many environmentalists believe we have toward the other species on this earth (we dramatically changed their environments and many are now dying off). In other words, just like how capitalism has an objective function (it works) and a subjective function (freedom), so too does environmentalism have objective (protects our environment) and subjective (maintaining the biodiversity of our planet).

Now the main reason I disagree with your premise that most environmentalists are selfish is that it doesn't really make sense when you look at time scales. Let's say everyone decided to just say: "fuck it, who gives a shit. Let's just ignore the environment and live our lives without worrying about any damage we may do to the planet (euphemism for living organisms, not actual ball of rock)." While we may see some negative effects in our lifetime, the majority of these negative issues would be felt by future generations. I always kinda liked this quote:

"Treat the earth well: it was not given to you by your parents, it was loaned to you by your children. We do not inherit the Earth from our Ancestors, we borrow it from our Children."

Now I understand that some people don't like being told what to do, so I try not to preach, but I do attempt to help the environment in my own actions and support politicians who try and enact "green" policies. But maybe that's just because I'm selfish ;)