@BillRM,
If there are threats made against Zimmerman then I am sure there are appropriate officials to deal with it. Since Zimmerman is not a public official I am not sure it is the federal government responsibility to protect him.
I almost feel that there no need to say this, but, as a matter of just stating my view, I don't condone or approve of threats against Zimmerman and don't think those making the threats have any rights to make them.
Having said that and meaning it, there is a need to look at stand your ground laws and other such issues relating to stop and frisk and things of that nature.