Every single time we have a mass shooting, like the one last week in Oregon, those against gun control take to the airwaves blaming mental illness. After all, anyone who wants to kill a bunch of people is clearly suffering from something. Sunday night on "Last Week Tonight," John Oliver decimated that myth with a harsh dose of reality policymakers are sure to hurriedly sweep under the government rug. "The aftermath of a mass shooting might actually be the worst time to talk about mental health," Oliver said.