“The Heathen Obama”? The limits to satire in American politics

Which I wish to remark
And my language is plain
That for ways that are dark
And for tricks that are vain,
The heathen Chinee is peculiar.
Which the same I would rise to explain.

Ah Sin was his name;
And I shall not deny
In regard to the same
What that name might imply,
But [...]