As an elected representative for the people of London, Ken should have some insults that are not 'Anti Semetic'.
Here are a few he could use, with out all the costs of the 'N' word:
You smell of piss
Your mum smells of piss
Your dad is a tramp
You have bad breath
The list of PC insults is endless.
Don't use an insult that will upset a small minority.
Use an insult that is wide reaching, you 'Spam Head'.