Your opinion about newsmedia was correct the whole time. This led you to ignore Mother Jones in 2012, but still your beliefs about the trends were correct for most of the time you held them.

What is the correct course of action?
Ignoring the newsmedia is clearly optimal. In particular paying attention to MJ writing on the same data set in 2012 would have produced the belief that spree killings had increased in 2006, an error according to your current MJ beliefs, though of course MJ doesn't notice the change. Maybe if you wait a few years, they'll convince you that nothing changed in 2011, only in 2015.