First, $13 million of the total was carried interest, which gets taxed like capital gains but is really just commissions that receive special treatment for no good reason. No profits taxes were paid on that income; right there, a minimally defensible tax code would have levied $2.6 million more in taxes on Romney.
I am completely agnostic as to the identity of the person in question -- it would be just as concerning if Barack Obama had millions in carried interest in his tax forms. The real question is how this exemption (which is commissions) can stimulate economic growth. I understand the argument for preferential treatment of capital gains. I even understand how capital gains can end up making moving between houses expensive for no really good reason. So I comprehend how this can be a matter of academic debate.
But can anyone explain why commissions should get preferential tax treatment?