I think the problem here is less the racists that run and more the lack of non-racists that don't!
The fact that someone can run uncontested means anyone can run and potentially win and that includes people with fringe ideologies.
And even in those races that are contested, if the people that are running opposite them are so weak ideological, so unelectable, that THESE sort of ideologies sound better, that they can't make a case AGAINST these sort of ideologies, then one thing to do is get better candidates and better ideologies to run against them.
After all, even in this article, it's only 20,000 people that got this guy on the ballot. 20,000 in a city of millions.