"A liberal who sometimes seems to shrink from the impact of his own findings"

You could say that. From the Financial Times :

When Robert Putnam published “Bowling Alone” six years ago, the book brought the Harvard professor such fame he was invited to speak at Camp David, 10 Downing Street - and Buckingham Palace ...

Now, after several years of further research, Putnam has come up with a more disturbing picture of contemporary American life: the more people of diverse ethnic backgrounds live in a community, the lower the level of trust among the community’s citizens.

This is, as he knows, an extremely contentious finding in a climate of growing concern about immigration in the US. It is potentially more controversial in Europe, which is struggling to cope with Islamic communities that can be actively hostile to Western democracy at their most extreme, and even in more moderate forms often prefer to live apart rather than integrate.

Putnam makes an important distinction between two different types of social capital: Bridging, in which an individual from one religious, ethnic, or class group, does something for someone in another group for an expected return, and bonding, when people who are “like us” – white Irish Catholic police officers, say, or black Alabama Baptist labourers – act in the expectation of a return.

The second kind, says Putnam, can “lead to Bosnia or Beirut” at most (I think he means 'at worst' - LT), and ever-wider social distance in wealthier societies.

It makes for close and warm relations among the “in” group but can freeze out or even make enemies of those considered “out”.

His diversity research reveals not just that bonding capital is strong and bridging capital weak in ethnically diverse communities, but also that both are weak in such societies: distrust permeates all relationships and people try to “minimise the hits on them from the society around them” by withdrawing into private space, often in front of a television.

That is a depressing picture ...

It certainly is. More here.

His research shows that the more diverse a community is, the less likely its inhabitants are to trust anyone – from their next-door neighbour to the mayor.

This is a contentious finding in the current climate of concern about the benefits of immigration. Professor Putnam told the Financial Times he had delayed publishing his research until he could develop proposals to compensate for the negative effects of diversity, saying it “would have been irresponsible to publish without that”.

The core message of the research was that, “in the presence of diversity, we hunker down”, he said. “We act like turtles. The effect of diversity is worse than had been imagined. And it’s not just that we don’t trust people who are not like us. In diverse communities, we don’t trust people who do look like us.”

Prof Putnam found trust was lowest in Los Angeles, “the most diverse human habitation in human history”, but his findings also held for rural South Dakota, where “diversity means inviting Swedes to a Norwegians’ picnic”.

When the data were adjusted for class, income and other factors, they showed that the more people of different races lived in the same community, the greater the loss of trust. “They don’t trust the local mayor, they don’t trust the local paper, they don’t trust other people and they don’t trust institutions,” said Prof Putnam. “The only thing there’s more of is protest marches and TV watching.”

British Home Office research has pointed in the same direction and Prof Putnam, now working with social scientists at Manchester University, said other European countries would be likely to have similar trends.

Hmm. His observations certainly fit well with a society where our rulers alternate 'we need more diversity, it's a strength, valuable contribution etc etc' with 'what's happened to political engagement ? Why does no-one get involved any more ?'

Naught for our comfort in the Sunday Times either, looking at our own LA - London. Our most diverse city - and one where you can be stabbed to death on a bus while everyone looks in the opposite direction.

Many peaceable residents, however, are being pushed out of the area. Carly, 25, a white telephone receptionist, said that every day during her 15-minute walk to and from work she tries to “make myself invisible”.