You know, I actually think that was a case of Obama realizing a mistake. When he said "that could have been me", he was commenting on the verdict of a jury by the man's peers. That undermines the trust in the legal system;
if it had happened in Jefferson's time he would have been impeached for obstruction of justice.
I suspect the behind closed doors protest from trial lawyers, most of whom are liberals, warned him off further idiocy. If he had not ventured into the Trayvor thing, then his absence in Ferguson would not have been an issue. I suggest that because he had in that and other personal tragedies, the 'wronged' in Ferguson felt he had a responsibility to them because he had done so before, and by his absence, then, infuriated things even more.
That's why I see him as a rookie, even now, six years in. He continues to play rock star/obamacare salesman without realizing there is 250 years of precedent.