I think it is normal for a country to help protect its citizenry, and certain violent aspects of human nature come up sometimes in society. It is the government's duty to help repress these basic instincts so that everyone can be safe in the public place. That means for certain minorities too.
One of the most enduring hates in this world is the hate of the Muslims against the Israelis, the United States, and many more locations. The older Jews remember the procession of events that led up to the Holocaust and they see signs of it everywhere, these days. I do as well. Not only do I think the Jews are in danger, I believe the Christians are, as well.
Yes, Jewish leaders need increased security. Honestly, the only person who can provide the security our world leaders need is God. There is no one else who can provide the type of security needed to protect the people who lead the population's votes, than God. It is only by his Grace that leaders are in the position they are currently in, and it is only by his Grace that they can be protected.
I can't help but feel that this feeling of being unsafe stems from Germany's history of harming jews. Assuming this is the case then it's the jewish leaders own paranoia that causes this feeling. I highly doubt that the Holocaust is going to go on repeat anytime soon. The modern values have changed and I feel the vast majority of people would protest a second Holocaust. Again, I find it highly unlikely that a country that has clearly reformed itself would so quickly turn around and start a second Holocaust so fast the leaders couldn't simply move to a new country.
The German government should treat all of its citizens equally. If individual citizens, such as the Jewish leaders, no longer feel safe, they should get the same level or protection any other citizen under distress would receive. If that is not sufficient, they can obtain their own private security or guards.