And to Think I can't See it on Mulberry Street -- Six Seuss Books retired for racism

There is one poem called “Cape Coloured Batman”. I’m finding references to it, but not the full text.

That’s odd - for me, the link goes to the Google Books preview that has the full poem (it’s not that long).

But perhaps a few lines will prove illustrative:

“This is the man the Empires made
From lesser breeds, the child of Trade
Left without hope in History’s shade;
Shouldered aside into any old place,
Damned from birth by the great disgrace,
A touch of the tar-brush in his face”

It’s a poem about Butler finding his batman drunk under a tree:

Nelson, my batman, the bastard, drunk.

Note that bastard here isn’t an ordinary pejorative, but a racist epithet.