Chemi Shalev captures the essence here.
By Israeli standards, Donald Trump’s designated Ambassador to Israel, David Friedman, is an extreme right-winger. He might find a place in the settler movement or with Naftali Bennett’s Habayit Hayehudi Party, but only on its right-wing fringes. He makes Benjamin Netanyahu seem like a left-wing defeatist. From where Friedman stands, most Israelis, never mind most American Jews, are more or less traitors.
Friedman has repeatedly attacked J Street, the pro-Israel, pro-Peace group, and its members as worse than the Jewish collaborators who served the Nazis during the Holocaust.
On the one hand, it's too hard for me to get too upset about the appointment of any Ambassador since Ambassadors don't make national policy. Anything they do of consequence only has lasting meaning because they are backed by the US government. But this suggests US policy in the Middle East will be guided by some mix of Adelson, Trump's impulsiveness and perhaps most critically Trump/Kushner clan politics. So it is as bad as it gets but mainly because Trump policy will be as bad as it gets.