One of the opinions common to the fundamentalist adherents of the world's religions and to most atheists is the idea that a religion's tenets need to be taken all-or-none. They say if you are to be a Catholic you must believe everything in the catechism and take every papal edict as true on faith, if you are to be a Muslim you must follow every teaching in the Koran and follow the fatwas of your Imam unquestioningly. Fundamentalists, I believe, do this out of laziness, because it is easier to swallow a pre-made world-view whole than to diligently construct one from the ground up based on your response to the data points you are exposed to in your daily life. In effect they surrender their rationality and let their religion think for them. The atheist motivation for this all-or-none thinking is also laziness, but in a different guise. It is a lot easier to argue against fundamentalist forms of religion, most of them contain self-contradictions and archaic and tribal teachings incompatible with the modern understanding of the world.
The thing is, almost nobody engages in this kind of all-or-none approach to religion. The average believer cherry picks those tenets of their religion which resonate with their inner understanding of the world. Many people engage in a systematic study of many world religions picking and choosing those aspects of each which suit them. They then assimilate these into their own unique, coherent world-view.
The atheist joins the fundamentalist in decrying this practice as somehow dishonest and irrational in one case or heretical and impure in the other, in either case fundamentally invalid. The atheist has no convincing arguments as to why he views the practice as invalid, other than that it makes it harder for him to denounce religion. Besides that they can only offer irrational arguments similar to those used by the fundamentalists: it's wrong because the scriptures say it is. But that's assuming the point you're supposed to be proving.
It is my opinion that even among the fundamentalists there is nearly nobody who swallows a religion's dogma whole, it would be necessary to turn off one's brain to do that. Considering that, it is required that we examine each teaching of the world's religions on its own merits. When we do that, along with the valid teachings and pearls of wisdom, we discover several moral teachings which may appear worthy at first glance, but when we consider their implications we discover that they are at least questionable if not downright immoral.
First, let's look at one teaching common to the three great monotheistic religions: that we should not worry about planning for our future or attending to our bodily needs because God, as our heavenly Father, will provide. As Jesus says, starting in Luke 12:22: "Therefore I say to you, do not worry about your life, what you will eat; nor about the body, what you will put on. Life is more than food, and the body is more than clothing.... And do not seek what you should eat or what you should drink...."
Or as Muhammad says in Surah At-Talaaq in the Quran "And whosoever fears Allah and keeps his duty to Him, He will make a way for him to get out (from every difficulty).And He will provide him from (sources) he never could imagine. And whosoever puts his trust in Allah, then He will suffice him."
As for the Old Testament, it is full of promises that God will provide, just look at the twenty-third Psalm: "The Lord is my shepherd; I shall not want."
On the surface this sounds like a holy precept, but one need not follow the implications of this belief too far to see where it is flawed. First of all, it encourages one to believe on faith without evidence in matters that are profoundly important. Second of all, it states something that isn't true; good and faithful people die of starvation and other forms of deprivation every minute. Third of all, if one really believes this what is to stop a poor person from having twenty kids and relying on God to feed and rear them? This point is on disastrous display in many poverty-stricken parts of the world. For example, in Pakistan, which is governed by an interpretation of sharia law, it is not only considered immoral but also illegal to consider one's poverty or other earthly matters in deciding when to have children. The only justification that Islamic law provides for delaying reproduction is if it will interfere with nursing the previous child for a full two years. The Quran considers it wrong to otherwise interrupt constant childbearing. The result of this is that most poor uneducated families have upwards of eight kids that they are unable to provide for. The solution to the problem generally seems to be the education of women. A clear inverse correlation can be shown between a woman's level of education and the number of children she has. For example, the fertility rate in Pakistan is around 3.9, the literacy rate around 54%, in Sri Lanka, where the literacy rate is 91% the fertility rate is 2.3.
It seems clear as women are educated they trade in their complete acceptance of Islam for the more rational approach of taking teachings based on their merits, and the change is reflected in their behavior.