It all depends on where we live and traditions and what the state decided as a philosophy of life.
For instance:
I live in Antwerp (Belgium) right in the middle of the jewish residential area. The jewish community is centuries old, is part of the prosperity of the town and has, with all the years formed a "community".
The recently (20 years or more) north africa immigrating population, has formed another community in another part of the city and there is therefore very little constant physical contacts between those communities and I've never witnessed any racial misconduct.
What has happened (a few months ago but less today) is vandalism on synagogues (broken windows, graffiti).

In France, the philosophy is about integration: you're first french before you're a catholic, a muslim or a jew. This is why "communautarism" or "communityism" is, according to the french current viewpoints, to be avoided as it is feared society will get split and split. Therefore, jews and muslims very often live right next to each other and because of the Middle East situation, the antisemitic feelings have radicalized and violence has erupted.
Then, there's the temperament (which is also why there's a rise in islamophobia) that doesn't arrange mutual respect.
I saw a debate between Nicolas Sarkozy and Tariq Ramadan on TV. Both are extremely eloquent. Ramadan is a muslim philosopher who's listened by the muslim moderates. Apparently, he holds a double language concerning antisemitism. He's exposing himself anyway and that's a good way to have him opt for desired choices.
About the islamic veil at school or for administrative reasons, Sarkozy (the french interior minister) got from him the acceptance that women should only wear a discreet ribbon (well I forget the exact word).
OTOH, Sarkozy is in favor of positive discrimination so that muslims can also get to higher responsability jobs and improve their life.

I don't know if it's more important to get integrated or to live in communities.
I know there are communities in Antwerp (a bit like London) and there's a Belgian community in Detroit Michigan.
Communities help keep cultural or religious traditions but they also keep people ,living in the same city, different from each other.

Tolerance is the key word.

Raoul