Dear Editor: Elian is finally back with his father and his father chose to return to Cuba. Protestors here threw rocks at the I.N.S., set fires in the street and blocked traffic on a major highway preventing people from going to work. There was no official condemnation of their acts. In Vieques protestors threw iron bars at U.S. sailors, injuring two. Again there was no official condemnation. The official silence concerning these despicable acts was deafening. John Broking Guttenberg Chief of Police (retired)