When you look at what a Jew is or not is it is clear a Jew is more than a race, a religion or a culture and the most accurate description that is suitable is being part of a family. Nothing else can describe the Jewish communities better as to how exactly they are connected. You might not feel connected to another Jew while you are still Jewish yourself, while most do feel that feeling of connectivity which is hard to describe or explain.
Popular rabbi Adin Steinsaltz explained that nicely in his book published in 2005 that all Jews should read called, We Jews: Who are We and What Should We Do. Not only in this book but around many literature are Jews called the Children of Israel, thus an extended family of each other? Thus is this something many celebrate and love, being part of a family which is the closets and truest description. Much like a family would, do you find Jewish not always agreeing, often criticizing each other and argue too. When times are tough they hold one another, comfort and everybody is held to highest possible standards. People outside should not be unfair against anyone inside the family as they stand united.
When one of the family are persecuted or suffers everybody share the pain while if someone does something immoral, illegal or shameful, it is also shared as they feel it reflects on the entire family and everyone feels the shame. Take an example for immoral and scandalous acts from people like Bernie Madoff, Jack Abramoff or Monica Lewinsky, even though all Jews disapprove, they were Jewish and the true Jewish family felt it reflected badly upon them too. At the same time will a great accomplishment from one Jew also reflect upon the rest of the Jewish Family and everybody left proud.