"To understand why, you need to examine the sources of government revenue. Last year about 80 percent of these revenues came from personal income taxes and payroll taxes. The mega-rich pay income taxes at a rate of 15 percent on most of their earnings but pay practically nothing in payroll taxes. It’s a different story for the middle class: typically, they fall into the 15 percent and 25 percent income tax brackets, and then are hit with heavy payroll taxes to boot."
Notice that he includes payroll taxes? Maybe you should stop while you are way behind, at least until you read the argument and understand what Warren Buffet is saying.
Now, if you want to change the system so that payroll taxes are "SS and Medicare with everyone paying the same rate" with no ceilings and on all types of income, hey, I'll support you 100%. Bring on SS / Medicare tax on capital gains! Here here! (Is that not what you meant?)