I think the the diversity of thought is an advantage for the survival of civilization in much the same way genetic diversity is an advantage for the survival of the species. But of course the difference between diversity and sectarian is acceptance, and this was a part of my explanation for why Christianity in my case.
In my very first introduction to this forum I said:
Many of us have cherished beliefs which we cannot prove to others and these can be categorized as religious – often difficult to compare since they tend to only address the questions which they are interested in. Yet we come to value a society which welcomes diverse religious perspectives and thus we need a way of governing a society which protects our liberty to pursue our own religious beliefs – this is the reason for secular rule. Surely it is obvious that our religious liberties must be limited by the same liberties of others and thus cannot extend to forcing our religious beliefs on others. So as long as the secular is acting to protect us from the excesses of religion then we must accept that our religious liberties only make sense when the demands of the secular are given precedence.
This was part of an explanation which also argued for the precedence of absolute over relative and objective over subjective.