"...a most despicable campaign in the UK General Election to oust a black Labour MP" Is the implication that somehow it's wrong to stand against a "black" politician, regardless of any political issues?

The argument George Galloway and most of her constituents had with Oonagh King was definitely nothing to do with her being black, it was primarily about the fact that she had supported the war on Iraq. And how many times when Tony Blair had been criticised about that had he said that it was up to people who disagreed with that war to show what they felt at the appropriate time, the General Election?