Dec. 26 — On the air, he has played the delicate role of referee to Israelis and Palestinians. In the midst of South Africa’s clash over apartheid, he brought Foreign Minister R.F. Botha and Archbishop Desmond M. Tutu into U.S. homes on the same television broadcast. But at home in Potomac, where he is building a massive riverfront estate on 16 acres of cattle pasture, Ted Koppel is at war with his neighbors.