Re: Copying Non-Muslims
Then he asked, that what sort of a society would they bring about if their most pious people couldn't marry three of four generations down you will have lower and lower calibre people because their most pious people died as spinsters or bachelors ...
Islam however, promotes the clergy to be married and all Muslims to heavily consider it.
Quality of a person is only partially genetic. And the proportion played by he genes in that has been coming down over time because of exposure. I will elaborate.
In the old times, a person was exposed a few small villages around where he was born and lived. Marriage, associations, trade, education everything happened in small clusters. So the proportion of external influences were small in comparison to genetic, family traits. In that situation, I can certainly see some possibility of that argument ...because upbringing in a atmosphere of 'piety' or whatever quality is likely to breed more of it.
But then the printing press, trains, planes, radio, TV and Internet all came along. Nobody is limited in information or external influence. Travel is cheap, settling in alien lands is common...under these circumstances, the environment is global and the role of immediate relatives, while still important, is only a fraction of what it used to be in old times.
That is why what you have referred to doesn't scale I think.
In fact in the current (and what has been for past several centuries) atmosphere those that take up the collar or priesthood voluntarily rather than because of family compulsion actually are mor pious...just like first generation immigrants work a lot harder than their children (in general that is). Because it is a transformation they themselves undertook and forced into circumstantially.
The other point I'd make is that Islam is not the only religion that allows marriage of their clergy. Hindu priests have regular family life (unless they undertake the sanyas or renunciation in which case they are not priests anymore); some christian denominations do not bar family life for clergy.