Ken Blackwell wrote an excellent piece explaining "Stand Your GRound" laws here:
I think it does a great job of explaining why they are a benefit and I think an overwhelming majority of Americans would agree. I think one problem though is few Americans understand how such laws work and the antis are using that confusion to lie about what Stand Your Ground laws cover.
They are essentially using deception to try and get people to make a choice (for or against Stand Your Ground Laws). If they can get them to make that choice, even uninformed, the chances that they will rationalize and continue to support that choice regardless of later information go up.