If I earn $6.75mm, then pay tax on it, I have $5mm.

Then I have $5mm in the bank and go get a job and earn another $100k, I'm only taxed (via income tax) on that $100k.

Similarly, if I have $5mm in the bank and it earns me $100k, I'm only taxed (via capital gains) on that $100k.

They are parallel taxes... not taxing the same money. The $100k is either earned income or investment income, and the $6.75mm was only ever earned income.

With dividends, it's easy to see that they are double taxed, but is that wrong? Your regular paycheck is double taxed too... first with income tax and then (in most states) with sales tax. There is nothing inherently amoral about double taxation, although it is kind of annoying how it hides your total tax rate.

To me, the annoyance of capital gains taxes is that it creates an entirely parallel tax rate structure, adding complexity (like everything Congress does with the tax code). If capital gains were treated like normal income, and capital losses (up to a certain amount) were treated like normal deductions, then taxes would be a lot easier for most people to file.

Same goes with sales tax. The fact that the government has turned every retail business in the country into a tax collector was an enormous coup. The system is impractical and a pain for businesses, placing the burden on them to raise funds for the states. It's also a massively regressive tax. Due to the impractical implementation, you can't even try to fix the regressive nature. States really need to find a better way to fund themselves.