Earlier quoted context omitted.
"most of us" don't understand the basic concept of marginal tax rates, and "most of us" don't understand the idea of marginal utility. "most of us" have in some form or another been doused in a firehose of "the only good tax rate is a lower tax rate" propaganda generated over (at least) the last 40 years. For a long time, the USA (like many other post-industrial revolution countries) has accepted that "fair" means us…
Most of us understand the concept of marginal tax rates just fine. We're arguing about the optimal shape of the curve. Everyone (with a few exceptions) seems to prefer that the curve should trend up sharply just past their own income level.
Closer to home: my kids don't understand it. My wife doesn't understand it. Most of my in-laws don't understand it.