The puzzle that Putnam and Campbell are trying to explain: how a country with high religious diversity and high religious devotion has such low religious conflict?
The answer is that we are not really very divided by religion. The secular tenth are the outliers on most measures. The moderately religious and the very religious are alike in most things.
On feeling thermometer measures - how warm (positive) toward Group X do you feel? - the results are a little unexpected:
Mainline Protestants, Catholics, and Jews are all liked by others at above average rates;
Evangelical Protestants and Nones a bit below average;
Mormons, Buddhists, and Muslims (in that order) are least liked.
In the end, ideology generates more animosity than religion does.