Steve King blows up at questioner who pressed him on the Pittsburgh massacre #IA04 pic.twitter.com/7sFQyY9fOW— Iowa Starting Line (@IAStartingLine) November 1, 2018
It is easy to prove Steve King's anti-semitic credentials. He endorses neo-Nazis, he basically says at Auschwitz "enough about the Jews," and on and on. So, when accused of being anti-semitic, he says he is pro-Israel. Which is not really an answer since one can be both anti-semitic and pro-Israel.
One might think that Israel is full of Jews and defines itself as a Jewish state that anti-semites can't be pro-Israel. That would be wrong because many folks who claim to be pro-Israel do so for a couple of reasons that have little to do with welfare of Jewish people:
a) They hate Iran enough that they see Israel as a useful tool against Iran
or more likely
b) They see a Jewish state in and around Jerusalem as a necessary condition for the biblical prophesy for the return of Jesus Christ. In which case, yes, Israel again is a tool and not something to be valued for the people who live there.
So, one can hate Jews, one can spout conspiracy theories about prominent Jews (George Soros now, the Rothschilds before) running the worlds, one can associate with Nazis and still consider themselves allies of Israel. Of course, the current leadership of Israel has done much to facilitate this by not confronting the hard right of the US, including Steve Bannon, "wooing" Viktor Orban who has been using anti-semitism in maintaining his increasingly authoritarian rule in Hungary.
Again, the key here is that one can claim to be pro-Israel and not be a philo-semite (to use the term I first heard used by a far right nationalist party in Romania). Using one's supposed "Pro-Israel" stances as a shield against accusations of anti-semitism is a strategy used by folks who want to have some semi-plausible deniability, but it is mostly an insincere response. Or an ignorant and insulting one as one simply conflates the Jewish people with Israel. Not all Jews are fans of current Israeli policy, and as the Orthodox types in Israel tend to assert, many Jews outside of Israel don't count.
Perhaps it is not widely known or considered how dumb an answer this is to accusations of anti-semitism, so we should call it out when we see it and hear it--that claiming to be pro-Israel is not a defense against accusations of anti-semitism. It should be as mocked as the "I can't be racist, I have a Black friend..." line.