Do you think trump and folks like him pay SS of Cap Gains or Carried interest? How about on loans against assets, a common way for a wealthy person to get cash flow? Nope.That's not exactly true. SS with holding tax is calculated separately from income tax in general. SE taxis also taxed differently than income generated from wages, or "other income".
I was SE most of my life, and I paid a much higher rate than my peers who had "wages". At the time looked at it as my duty to have my freedom tax. Now I think I was just being penalized for not becoming a corporation, or more likely a non-profit org.