The main reason is that he spreads vile and hateful lies against Jewish people, and not because he is anti-Israel. He has been reported to repeat the blood libel to his followers. Since you are morons I will explain - he has stated that jewish people use non-jewish childrens' blood to make unleavened bread for passover. If you don't find that disgusting, I think you have no hope. Now, in israel he is actually citizen so he is free to say what he likes (within limits) but the logic doesn't follow that the Brits are required to allow him in.
Report: Car bomb kills 10 in Syrian port city (AP)