MSNBC Chief Legal Correspondent Ari Melber breaks down how the Trump administration is trying to thwart requests for truthful testimony about matters ranging from the Mueller probe, to separate matters like national security oversight. Former Trump staffer J. W. Verret tells Ari Melber why the Mueller report was a turning point for him, saying it clearly documents “up to 12 cases of obstruction of justice” and Trump should be impeached.