Listen to Rabbi Kahane debate him. It's a great audio.
I have heard it. Lenni Brenner is more evil, than I thought before.
He says in the radioshow, that he is a marxist and that he don't care about religion. But then he was hired by Neturei Karta and went to Syria, to tell the world, that the Jews are fine in Syria.
He defended the praxis, that when Syrian Jews go to other countries, one relative must stay in Syria. So the Syrian Jews have to come back, when they don't want that the MoSSlems do something evil to their hostage child, mother, father, brother.
He knows this facts, but mentioned in this Radioshow, that the Jews in Syria were well threated.
In my oppinion Lenni Brenner is totally nuts. He belongs to a mental-asylum.