The government decides to try to increase the middle class by subsidizing things that middle class people have: If middle-class people go to college and own homes, then surely if more people go to college and own homes, we’ll have more middle-class people. But homeownership and college aren’t causes of middle-class status, they’re markers for possessing the kinds of traits — self-discipline, the ability to defer gratification, etc. — that let you enter, and stay, in the middle class. Subsidizing the markers doesn’t produce the traits; if anything, it undermines them.
When people say things like "don't let this moment pass without acting on gun control," what they're really saying is our arguments are so unpersuasive that they can only succeed when people aren't thinking clearly.