There is a reason the Bible says you can only lend at interest to a stranger, not to one of your own.
Xenophobia ?
And yes, I do realize that the common wisdom of human (pre) history was about survival of small groups, with occasional encounters, violent or otherwise, with other such groups. Still, I found the apparent reliance on perceived authority amusing in a context where it makes it appear in the opposite way as religious authorities would like it to appear nowadays
