Honestly this thread is depressing.
The reason rappers use it is an attempt to reclaim it from the being a term of abuse. To take away that power.
A white man using it in a humourless context is not the same.
The rhyme refers to a time when ethnic minorities were viewed as sub human. FFS the next line is 'if it squeals let it go'.
How can you not see why it is so offensive? How can you think it's just an innocuous nursery rhyme?
The bridge incident in my view was even worse. I didn't know it was a term of abuse either but Clarkson clearly did. The glee of 'aren't I clever getting this one past' is obvious.
Top Gear is the BBC'a biggest export and it is shown in countries that would find it incredibly offensive - from a time when people in living memory were killed and abused by the people who used it.
It's not the 'PC police' who need to grow up.