Priests aren't allow to associate with sinners

 There's a good story in the Bible about how aghast the Pharisees were with the idea that a righteous prophet could ever been seen to associate with lowly sinners. Jesus couldn't be righteous because of his associations with the 'wrong' type of folk.

It is really hard not to see current purity purges in our newly hyper-moralized institutions in the same light.

The most interesting thing is to see what the right level of analysis is so you can see the gene-cultural Darwin machines that produce the commonalities but which also give rise to surface differences.  That's why strange attractor topologies are so interesting...