Some poetry

What's "wrong" with this poem by Benjamin Zephaniah? What particular "phenomenon" affect some of the words? Why do you think the author did that?
Send your ideas as comments here or to your class's gmail adress.

White Comedy

I waz whitemailed

By a white witch,

Wid white magic

An white lies,

Branded by a white sheep

I slaved as a whitesmith

Near a white spot

Where I suffered whitewater fever.

Whitelisted as a whiteleg

I waz in de white book

As a master of white art,

It waz like white death. 

People called me white jack

Some hailed me as a white wog,

So I joined de white watch

Trained as a white guard

Lived off the white economy.

Caught and beaten by de whiteshirts

I waz condemned to a white mass,

Don't worry,

I shall be writing to de Black House. 

Benjamin Zephaniah