Please Help Me Understand

President Biden has proposed increasing the rate at which capital gains are taxed on anyone earning more than $1m a year. That’s .3% of people or 3 in 1,000.

Why are so many of the 99.7% of people for whom the tax increase is completely irrelevant so upset at the proposal?

What’s the principle at work? Millionaires are an aggrieved group who deserve a break from people of ordinary means?