The only thing that would change the situation is if the Trayvon had a legal protective order against Zimmerman.
If someone was stalking my daughter then certainly there would be a legal protective order applied requiring the person to stay away from my daughter by X number of feet, etc. I don't know how it is in other states -- but if someone violates a protective order here and appears threatening -- then you are legally permitted to use a firearm to defend yourself.
Our community has a neighborhood watch. I can assure you that the individuals in charge of our neighborhood watch would definitely follow any suspicious character in our neighborhood while on the phone with 911. If the suspicious character attacked them -- well lets just say that all of the neighborhood watch leaders generally have concealed carry permits.