Tons of people have died for a variety of causes throughout human history. It does not mean that the causes were not silly or deluded. (e.g religious wars, Communism, Fascism etc.)
Carlin didn’t say it was silly, he said it didn’t matter. Religion, communism, fascism were all world-defining ideas, and they very much mattered to those who fought for them and against them. What am I saying, “mattered”. Go check social media, they matter right now.