All of these sorts of facts are manipulable and/or not easily knowable. > - whether crime is up or down Manipulable by the agencies that keep track of and pub

All of these sorts of facts are manipulable and/or not easily knowable. > - whether crime is up or down Manipulable by the agencies that keep track of and publish those stats. Governments often manipulate these. > - whether the earth is warming or not There is a huge amount of controversy in climate science. Check the "Climate Gate" files from 2009 for example. Check out the controversies over weather station siting for another. > - how many people live in poverty Poverty levels vary with time and by country, and are typically set by governments. People often disagree as to what defines poverty. Poverty stats are manipulable. > - what the rate of inflation is You should look into what Argentina did around 2012. > - how much social security or healthcare costs The figures from the budget are not controversial. How much healthcare spending is wasteful is a completely different matter. Quality of healthcare is also very much subject to debate. > These are all verifiable, measurable facts, and yet, we somehow manage to disagree. They are not easily verifiable because they are mostly susceptible to manipulation. Therefore it's not surprising that people disagree. > [...] And that leads to an total inability of having any discussion at all. No, it means that discussion might have to start with the fact that there is disagreement as to facts and then you can have an open discussion about why, what is being done to prevent consensus forming as to those "facts", what needs to change to make that possible, etc.