Jackie Mason was a member of another forum I was a part of. It was called the United America Committee, which had VERY similar goals to the JTF, and was very supportive of Israel. I chatted with him a few times, and he was incredibly supportive of Israel, but wouldn't specifically say he was supportive of Kahanism. I guess its a third rail for any high profile people to openly support Kahanism.
John Voight is the most supportive high profile gentile Ive ever heard from; and I assume he would also not openly support Kahanism.
Ive heard a couple mainstream conservatives brush off Kahanism as an extremist movement, including Michael Medved.