So explaining why he had sympathy with a family that had lost someone is related to this... How?
There are hundred of young children who die every single day. Many die violent deaths. More than a few are shot.
Obama jumped in the middle of what some people were turning into a race issue before he knew the whole story.
Saying the M/Z incident was a tragedy for all involved is obviously a correct thing to say. Saying if he had a son, it could be Trayvon is incorrect unless you think the president would actually raise a son who used drugs, was a thief, got in fights, and got suspended from school.
He didn't just show sympathy, he took a side. And that side, as evidence has shown, was the wrong side.