Oh the irony. The Tea Party was formed in direct response to the corporate welfare and crony Capitalism that came out of the end of the Bush Administration and the beginning of the Obama Administration. One of the main tenants of Nazism is crony Capitalism.
His analogy at first has some small merrit comparing small groups that get more support over time. As his comments continued to make the equivocation that both nazi and tea were crazy then he stepped well beyond a conceptual metaphor and applied the time honored concept of defamation.