Obama dummy hanging from Carter sign?

So here's the story:

"PLAINS, Ga.-- A spokesman for the U.S. Secret Service says the agency is investigating an effigy of President Barack Obama found hanging from a building in the hometown of former President Jimmy Carter.

Secret Service spokesman Ed Donovan told The Associated Press that the large black doll was found Saturday morning along Main Street in the small town of Plains.

According to footage from WALB-TV, the doll was hanging by a noose in front of a red, white and blue sign that says "Plains, Georgia. Home of Jimmy Carter, our 39th President." A witness told the television station that the doll wore a sign with Obama's name on it.

Donovan said the doll was removed Saturday. He declined further comment.

Sumter County Sheriff's Department officials declined comment, referring all calls to the Secret Service."

The question I have is, unless there was a specific threat, why is the Secret Service investigating an obvious display of free speech?

Of all the places to do this though, in the town where Carter is from. I think this is more than likely nothing more than a vast Left Wing Conspiracy directed at stirring up another race war. What do you think?