AFAIK there is no reason to oppose incest from a secular perspective ... that is why secular countries in europe are thinking of decriminalizing it, i.e., government would have no interference in that matter unless mutual consent is not there in which case it would be treated just like any other sexual-assault ...
However Islam also doesn't consider incest any worse than sexual relationship between unrelated man and woman ... our increased disgust towards this act (compared to regular adultery) is the result of our culture, tradition, and psychology ... I don't think it has anything to do with religion (unless anyone has references from Quran/Hadith indicating otherwise)