I was going to say this earlier, but chose not to since I didn't think anyone else would actually think income vs. adjusted gross income made much difference when the man donated over $4MM, but I guess I was wrong. Tithing in the LDS church is 10% of your increase. So at least 10% of that 13.45% has nothing to do with deductions on his house, dependents, or even Ann's horse.
I see the point you're trying to make about capital gains tax, but it's not like the tax only benefits people worth $1MM or more. Also, how did these people get their money to invest? At some point, whether it was an ancestor or themselves, someone had to work to obtain that money. Furthermore, it's not like there isn't any risk involved in investing. People can and do end up worse off than if they hadn't invested at all. Yeah, the people with money benefit from the rule and those who don't have expendable cash don't, but it's not like the rule takes money out of the pocket of the financially needy.