"We, US citizens, collectively get to define what is US national interest and we believe in support for Israel. You may not support it, but I need not justify myself to you on patriotic grounds." You have the legal right to do that. I think he has the legal right to say you're a traitor to the USA. You have no requirement to justify yourself, but for PR purposes it might make sense for you to provide some sort of rationale to say it isn't treason. "USS Liberty was judged by a US investigation to have been an accident." That is a convenient lie the US investigation agreed to, because it was inconvenient to admit the truth. That ship was in a place it had no business being, and Israel had repeatedly demanded that it be ordered away. Israel had every right to sink it. But accident? People don't machine-gun other people's liferafts by accident!
Defense Ministry says had no knowledge of alleged improper defense deals by Gal Hirsch (Haaretz)
from the article: U.S.-Israel row clouds opening day of AIPAC conference