Buchanan is not a Conservative even though he shares some positions with some Conservatives. Conservatives don't align with Marxists, nor do they come down against Israel and against Jews without exception.
Buchanan is not a Conservative I don't know where you have been, but Pat is a old school conservative in most peoples book, regardless of his positions on a Jewish state.
As he has stated many times, "I have not left the party, the party has left me."