I think we have to fundamentally change how the party system works if we're going to get people in politics for the right reasons in general, but especially in local politics. There's no reason that the people collecting bins, filling potholes, and providing essential services along those lines need to be associated with the moral abattoirs that are the national political parties for example, at least in my experience these local politicians are voted on based on an area's national political inclinations rather than any individual merit which lets all sorts of lunatics in. The first thing we need to do is break this link and make local government completely non-partisan.
I wish there was an empirical way of screening out moral puritan types with the aim of directly eliminating their influence, but I'm not sure that can be done without endangering democracy itself. A more difficult but much more ethical approach I think is to try and create new social norms that make aggressive conformity something to be ashamed rather than proud of, puritanism in any direction should be made into a sign of weakness rather than strength. We need a society that instinctively defends "witches" when the witch-hunters are in town.