In Islam, everything is “malum prohibitum” as opposed to “malum in se.” That is, things are considered wrong only because they are prohibited, not wrong because they are in and of themselves bad.
Eating with your left hand is wrong in Islam for no other than that Muhammad said not to do it. And for a Muslim, that is enough. Islam is essentially a giant game of celestial “Simon Says,” with Allah (read Muhammad) acting as Simon. Simon says enter the bathroom with your left foot. Simon says kill gays.
In turn, the need, and even the capacity, to distinguish right from wrong is completely lost in the believer. Things that would normally make a person cringe and throw up are said and done by a believer without batting an eye. At the same time, normal, benign activities are seen as intrinsically evil.
Sexual slavery? No problem! Having your trousers below your ankles? Bad! Bad, bad, bad!!
Exactly what I've always been thinking! In Islam (as in many other religions), there are certain prohibitions that are ridiculously arbitrary; serve no purpose; and make no sense. The ankles/pants thing, the lying on your stomach thing, the stepping into the bathroom with your left foot thing, etc.; those things are all benign and morally neutral to most normal people but Islam -- for no particular reason -- has rules, and makes a big deal, about them. OTOH, the slavery, homophobia, sexism (including outright physical and sexual violence against women) and wanton killing are a-okay, and sometimes even considered moral and commendable. To top it off, Islam even prohibits some morally *good* things (eg: adoption).
When debating with Muslims/theists they always bring up morality. "How do you know murder is wrong?" I hate that! I usually respond with "Well, I obviously know murder is wrong because…it is just fucking wrong, okay! Would you be killing people for the sake of it if your collection of ancient desert ratings didn't tell you it was wrong?"
Where do we derive morality from? I know I have it; there are certain things that just make my insides scream "this is WRONG!" but where does our sense of right and wrong come from? Parents? Culture? Socialisation? Innate?
When you really think about it, a lot of Muslims don't even derive their ethics/morals from Islam. Most will tell you sex slavery is wrong despite the Quran saying the contrary; most don't know what the Quran says on the matter but still know that sex slavery is simply wrong. The savvier, more knowledgeable liberal Muslims perform all kinds of mental acrobatics to come to the conclusion that the Quran is not actually saying what it is actually saying in plain text…so as to bring it in line with their morality. That makes me think morality is probably innate.