By: Mark Glennon*   Detroit last week gave us a glimpse of what to expect on a much larger scale in Chicago and across the country as the sheets are gradually pulled off on public pensions.   Reality ultimately invalidates wrong assumptions. In the public pension world, that means taxpayer liabilities eventually will spike. Scapegoats will be found, fairly or not. Lawsuits will come. Heads must roll as anger erupts — all financial meltdowns are that way. Officeholders and voters bear primary responsibility, but that won’t matter.   Detroit’s mayor announced the startling (to some) conclusion that the city’s