It's obvious. If questioned by someone who has an inkling about economics and how things actually work, their bumper-sticker policies won't work.
Walz's 'more housing means lower taxes' might work in a very small town trying to buy a fire engine, but overall,it means greater demand for city type services (because he's not talking buying 40 acres and a mule, but urban/suburban housing) like water, sewer, snow removal, sidewalks and streets, not to mention police, fire, and EMS. The more of that needed, the more it will cost to maintain, (not just to purchase the needed equipment/infrastructure). If more housing meant lower property taxes, then mine would be half what they were 30 years ago, not more than double.